I recently upgraded to version 1.1.5 Build 2643 (64-Bit) version of GreenShot. I can no longer get the print screen (or f11) to work. I am running a 64-bit version of Windows 7 Professional. I can get the capture to work if I use the capture Region option from the pop-up menu.
I have a secondary machine with the same OS, but using version 0.8.0 Build 0627 that works just fine.