Got it right from here. Played it on WinVice 3.1 x86 (in NTSC mode). It hasn't happened since, though. It might have been just a fluke.
Emulators are programs and as such they can contain bugs. Just see the long list of "Known bugs" on the VICE website. Also, version 3.1 is now a bit old, as they have reached 3.6.
Quite right. Most probably a VICE issue, since you've checked and double checked the game code.
