App version download error: couldn't get input files: application name

You'll come across this error when the project has released new applications but their encryption isn't known yet.
It's also possible that BOINC couldn't download the signature on the file it has downloaded, therefore it cannot check if the encryption on the file is the correct one. BOINC won't run files it cannot check, or that have a wrong signature.

Do post the error on the project forums.
It may also help at times to reset the project. BOINC uses a public key to checks the encryption signature of all downloaded files from that project against. It's possible this key got corrupted, and resetting the project will force a new download of that key, fixing the problem.