Between which versions?
These are the dlls that were changed (and now reverted). Green is current installed version, red is newest version.
Don't forget the database schema can get updated through versions too so you could try rolling back to a back up version of the DB from before the upgrade.
Thanks for your comment. The DB updates are done manually and were not necessary in this upgrade.
Some seemingly random uninstalls / installs of EPIServer dll's fixed my problems. Not a very satisfying solution.
Probably a dll with wrong version somewhere then...
On our site we use XForm for form implementations. We did some upgrades to EPIServer dll's and now we get an error we trying to select another form:
I tried to revert the DLLs back to the latest working version but the error remains.