We ran into a few strange issues today where we had applications like Word, Excel and Adobe Reader that would not open any of their associated files. We also had reports that network printing was not working correctly either.
After much trial and error, we finally discovered that the reason for this was a Microsoft Update released under KB5005565. After we uninstalled this update, everything worked fine and multiple computers.
Uninstalling the update is not really a final solution so we are hoping that Microsoft resolves this soon and release a new fixed update in its place.