I've had like 1 but that was several nightly's ago. Which version are you on, stable CM7, or nightly. You may need to just rewipe everything (twice just to be sure) then reflash whichever version of CM7 you like.
Or try a different kernel.
I'm using nightly #41 and its really fast! No reboots during a full day of use. Also flashed the latest Tiamat kernel thats on page one of this post late yesterday and so far I'm really liking what I see.