Grayed out folder won't open in finder
I had the same issue with an account folder, which I restored from a backup via rsync. The problem seemed to be the corrupt or missing creation date. After setting it manually the folder was acting normal again. I used the SetFile command from XCode's command line tools. So this should solve the issue:

SetFile -d '12/31/1999 23:59:59' will-not-open