OK, I don't know if I get you right, but you could first use modaco No Data to disable the data connection. Search for it here in the forum!
So this should force Opera to use the wifi if it is switched on! And see if it works.
Second, what Pda, Eboot, Phone version do you have?
I also had the problem that I could not use my wifi correctly. i updated my device (PDA,Eboot,Phone without CSC) to the newest official 6.5 version!
And after that I'm now able to use my wifi! Not as good as it should be, because I still have problems with the router, but i can tell that it works now!
So maybe you could try this also!
I don't know how much you know about your device so far, as you seem to be a new owner
Go to the B7610 Collection thread here in the Forum(Its a sticky) and read about flashing and and updating your device! This helps a lot!