Download GPS status from the market. You can re-download the GPS data. It will lock in seconds after you do that.
i've been running CM6 since it went final, and did not have this problem until yesterday? i can't figure out why it started all of a sudden. the only weird thing i did was install that google maps BRUT mod, and then uninstall it. i also switched to cvpcs kernel a week ago, but i'm pretty sure it had worked fine after that.