URL rewriting for trackbacks (wp 1.5.2)

I bet this is a much talked about problem, but due to the nature of the words involved its quite hard to find the solution on the forums.

The trackbacks my WP (1.5.2) are in the ?p=123 format, although I do use url rewriting. How can I change this? Upgrading to WP 2 is something I have planned, but it will take some time since I severly damaged my theme by changing stuff in includes etc. ??

Thanks in advance for some tips or solutions.