You have to use q to quit git’s pager. Using Ctrl-C only causes problems on windows.
Ctrl-C should not quit the pager (and it does not on a linux system). When you Ctrl-C on windows (msysgit I suppose?), you are somehow killing the process “from the outside” (i.e. from cmd.exe). I don’t know the exact reasons why this happens.
As I’ve experienced similar problems in the past: try to hit q and Ctrl-C repeatedly in random order, if you’re lucky you’ll get a working prompt back again 😉 [There’s no better solution I know of – but it worked for me …]