I opened a CS5 library-file into InDesign CS5.5.
Then InDesign quits.
I started InDesign again, all (old) documents opened as Untiteld.
Than I got an error that InDesign it is not a legal name for the Library.
And InDesign quits again.
I removed the preferences.
I deinstalled InDesign
and installed it again, but I get the same error.
How can I fix this problem?
It's not clear if you tried to open the library again, but if you didn't and ID quit after opening the other files, it sounds like some of the recovery data is preventing ID from restarting. I don't know any way to identify which part of the recovery folder content is which file, so you should remove all of it, then add back one at a time if necessary to recover some other file, but if you have recently saved versions I think I'd probably abandon the recovery data entirely.