I'd check with these guys in Canada since they are the only qualified and experienced Vitus (and other) frame repair service I know of:
http://www.guywires.com/salestuff/vitusparts.htm
If they tell you to junk it...it may well be toast. I've had some critical aluminum alloy parts crack-repaired by a really expert TiG welder who specialized in just this sort of thing for alloy auto and motorcycle wheels (where your life can be at stake). If such a welder won't do it, it's because it can't be repaired with certainty so as to guarantee strength...you wouldn't want to ride it even if it might look OK.