Option 1 Solution
Delete the Frmcache.dat from the location as stated below :
C:\Documents and Settings\user_profile\Local Settings\Application Data\Microsoft\FORMS
To Delete the Frmcache.dat File
Close Outlook
Click Start , point to Find , and click Files or Folders .
Type “Frmcache.dat “in the Named box, and click Find Now .
Click to select the file and press DELETE to remove each instance of the file.
Restart Outlook
Option 2 Solution
Use the ForceFormReload registry key
When the forms cache seems to cause problems sporadically, and you cannot determine the cause of the problem, you can to set the ForceFormReload registry key in Outlook. When the ForceFormReload registry key is enabled, and Outlook encounters an error when opening an item that is based on a custom form, Outlook automatically clears the cache for this specific form.
Then, Outlook tries to open the item again. While this method does not correct the cause of the forms cache problem, this method does make the problem transparent to people who use custom forms.
To enable the ForceFormReload registry key functionality, follow these steps:
Start Registry Editor.
Click the following key in the registry:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\11.0\Outlook
On the Edit menu, click Add Value, and then add the following registry value
Value : ForceFormReload
Data Value : Reg_Dword
Value Data : 1
Quit registry
Signing Off Now
jMs
We share what you might need? 
Very smart and comprehensive approach to solving the problem. I read more than 13 articles and none understood the problem. It seems all copied from Microsoft articles to remove the FrmCache.dat files, which I couldn’t find. Your article represent a deep understanding to how Outlook works and to the root of the issue. Your consice and direct approach to the solution is even greater. Good luck and all the best in your research finding great solutions to common problems.
Excellent article – it has resolved my issue completely!
I have followed the steps but could not find either the Frmcache.dat file. I’m assuming that might be one of my problems. Where do i go from here?
Yes, the explanation was quite helpful, especially the alternative of setting the ForceFormReload because it means that other less techy users of my computer will not be bothered or bother me.
Mike : Most likely your computer is not configured to show hidden folders.
For you to unhide those hidden folder , do follow the steps below:-
open My Computer => Tools => Folder Option => View => Hidden files and folders , check on the radio box “Show Hidden Files and Folders”.
After this step, do locate the path again, you should be able to locate the frmcache.dat
Problem:
Outlook error: “The form required to view this message cannot be displayed”
Solution:
With Outlook Open,
Click TOOLS –> Options –> Other –> Advanced Options –> Customer Forms –> Manage Forms–> Clear Cache
Should Solve Problem.
Eddie at BidDay.com
Wow, this actually worked. I had found lots of other solutions that didn’t do anything, so thanks!
Great solution. It saved my long waiting time from our support team
I have to say it worked just right for me. I did have a problem for a second with it not searching hidden folders. Thanks!!
Thanks Eddie, your solution worked first try. I tried the first few suggestions and none worked.
Thanks for this advice. It not only fixed this particular issue, but also resolved a problem with ActiveSync which gave an error: “The following appointment cannot be written to Microsoft Outlook due to error 80040119. The item will be skipped.”
Tried the reload forms Registry entry and the old message went away to be replaced by “The object could not be found.” Also tried manually clearing the forms cache and a search didn’t find the frmcache.dat file…
Solution #1 worked like a charm. Both of our network guys had no idea how to fix this:)
Excellent: I have searched for the solution previously with no avail – Thank much
The first option worked fine. I’ve been pulling my hair out for the past two weeks looking for a solution between installing and uninstalling outlook.
Thanks !!!!
This could also be an issue where the Outloo.exe process is still running even though the application was closed out. That fixed my issue the others did not so you may want to add this solution as well.
Excellent …. got my problem solved! THANK YOU.
Just clearing the cache as Eddie said worked for me!
Thanks, Solution 1 worked
Great solution, worked like a charm. Thanks so much for posting this solution, straight forward and to the point.
Eddie, it worked great. Thanks.
First off thanks for the input. I have tried deleting the frmcache.dat before and that did not work. Used the ForceFormReload and it didn’t work either. So went back to re-deleted the frmcache.dat then cleared the cache under tools then tried it and it worked. Thanks
Option 1 worked flawlessly, done in 2 minutes.
Resolution on Microsoft site didn’t work and was misleading.
Eddie’s solution worked for me, Thanks Ed
The first suggestion worked for me! Awesome! Thanks for sharing!
Very clear instructions, thanks! I used solution 1.
Removed and readded the user’s outlook profile and that error did not come back. Our usual fix for Outlook problems.
Option one worked great for me! Thank you… been dealing with this since I upgraded from MSO 2003.
Jay
Thanks, this is just what I needed. Quick and simple solution. Worked first time.
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Great work. Solution one worked. I tried Eddie’s solution first. That didn’t work.
Thanks
Thanks a lot. It worked
My problems started straight after installing Nokia PC suite
option 1 worked for me thanks.
I found a solution in Microsoft’s website.
It was pretty easy. Easier than to edit the registry.
http://support.microsoft.com/kb/839804
I tried clearing the form cache with this method…
Clear the forms cache
There are different methods that you can use to clear the Outlook forms cache. Each method has advantages and disadvantages.
• Method 1
Microsoft recommends that you use the Clear Cache method. To do this, follow these steps:
1. On the Tools menu, click Options, and then click the Other tab.
2. Click Advanced Options.
3. In the Advanced Options box, click Custom Forms.
4. In the Custom Forms box, click Manage Forms.
5. In the Forms Manager box, click Clear Cache.
It work great. I hope it is useful
The Microsoft website was not helpful.
Tried repairing and re-installing. No luck.
Your answer to the problem worked in 2 minutes.
Thanks.
Great job. Solution 1 worked like a charm
Thanks
GREAT solution. The first option itself worked for me. For users who couldn’t find the “Application Data” folder, this folder might have slightly different names depending on the OS that you have. For example, in Windows 7 this is “AppData”, but you’ll need to enable “view hidden files” in your File explorer to see this folder; it’s a system hidden folder.
Thanks,
Saurabh
Thank you so much. I had created a custom Outlook Task that was crucial to my keeping track of deals at work. I was in a panic and couldn’t find a solution–until I found jMs’ advice. It is 2016, and the solution works still. jMs, I hope all is going well for you.