Last week I finally finished upgrading my blog to Kentico 10 and moved it to Azure. While the upgrade procedure went pretty smooth, there was one issue that popped up when trying to view items in the content tree.
After investigation and with the help of Kentico support, the cause of the issue seemed to be related to an earlier upgrade process. I initially started my blog in Kentico 4.1 and have upgraded it to the newest versions ever since :)
Here are two screenshots showing the issue:
The next step was checking the event log for some more info. The entry contained the following stack trace:
From the first line stating "GetClassName" in combination with the error "Page type class not found in the data", I assumed that there is an inconsistency in the data somewhere. Time for some (SQL) digging!
To make a long story short, I noticed that the [CMS_VersionHistory] table contained references to old ClassIDs that didn't exist anymore. Running the following update query fixed it:
UPDATE [CMS_VersionHistory] SET [NodeXML] = REPLACE([NodeXML], '<NodeClassID>2031</NodeClassID>', '<NodeClassID>4495</NodeClassID>')
Hope this helps!