(GnuPG 2.0.20, Windows 7 Enterprise, SP1)
In the GPA, in the Clipboard Window, after hitting Decrypt, the program will 
hang until it gets terminated by the OS ("A problem has prevented the correct 
running of the problem", or similar, I'm using a german Windows).
The passphrase dialog appears, so the bug seems to occur in the actual 
decryption phase.