I have Viking 184.108.40.206 installed on Windows XP SP3. I observed this behavior with all previous versions also.
I have a map layer (Openstreetmap Mapnik) with "Autodownload / Use Viking Zoom Level".
When I then draw a track and move the map by "Middle Mouse / Click and Drag", I frequently get runtime error as shown in attachment.
When I disable "Autodownload", the crashes vanish.
Interesting observation: For this ticket, I tried to make Screen Video of the effect. Recording screen video makes my PC quite slow. That way slowed down, I could not reproduce the crash even with the wildest moves in Viking, but when I stopped the screen recording, I had it instantly. So it's likely a timing issue in Viking.