Hi Fiero and welcome.
Yeah I've seen that error before. Someone else with a TNT2 gfx card reported the problem. We looked into it and apparently it's something to do with the card/drivers and there's nothing we can really do about it I'm afraid. Even if you don't have the same gfx card it looks like the same issue.
The new version of mono has a completely different background routine so might be ok (when it's released
) but there's nothing I can do with the current version. Sorry.