A lot of cooks found the problem in the rilphone.dll, but I think it need to be cooked in and can't just be replaced. Maybe a hard reset would help. Is there a reason you didn't change to a cooked ROM? If you flash a radio, you can EASILY flash a ROM. I like Groove's and Calcu's stuff, but all the ROMs have advantages. Just read the thread and see what you like most.
It took me more than a year to get up the nerve to flash .. even a radio. Check out rstoyguy's threads. He has great tutorials.
But if you're not looking for a new ROM, try a hard reset to see if it helps.
