When I do a screehsot via alt-prtscr (capture window) when firefox is the active window, the resulting screenshot is black no matter what is in the active tab. Full screen capture works fine.
Environment
Windows XP x32, FireFox 35.0.1 (latest) all add-ons up-to-date
I have the same issue in 1.2.6, and it only seems to be a problem if I use the Alt+Prnt Scrn button to take a screenshot of just the active window, but if I click the tray icon to do so, it works fine.
When I do a screehsot via alt-prtscr (capture window) when firefox is the active window, the resulting screenshot is black no matter what is in the active tab. Full screen capture works fine.