Problem: the boat always like to round up against the wind strongly

I am an owner of a Omega 34.

Fantastic sailing boat, but the problem I have is that the boat always like to round up against the wind strongly with 4 beaufort or more. I have a new mainsail, the mast straight up (not backwards) and even then the boat likes to turn up against the wind.

I have found 2 tests of an Omega 34 (Laettseglad och enkel 6/97 and Foer Segel 1994). Both are not in English and connot read this.

Can anybody tell me more about this ?

RobertVolker / HOLLAND