Problem: after importing messages from Windows Mail to Outlook, you receive the following error message when reading email:
The custom form cannot be opened. Outlook will use an Outlook form instead. The object could not be found.
This shows up with each message imported into Outlook 2010 from Windows Live Mail. After clicking OK the popup disappears and you can read the email, but the popup is annoying.
Fortunately the fix is fairly simple: You need change the form (message class) associated with the messages to the IPM.Note. To do this, download DocMessageClass and run it on the Inbox (and any other affected folders).