Put Mac to Sleep... Wakes up 20 min Later

Sorry to ask a possible repeat question; I cannot get the search to work.

When I put my MBP to sleep each night, about 20 minutes afterwards, I hear the CD drive fidget (I think), the screen flashes on, the computer seems to freak out for a bit, then goes back to sleep.

Any ideas?

Ye, same here, it just happens sooner with my mbp, like 30s after I put it to sleep. It doesn't really bother me, but it'd be nice if it could be solved.
And it only happens when there's a disc inside.

bump?

Could try reseting the SMC.

May be normal?
http://docs.info.apple.com/article.html?artnum=305478

Check the logs in Console. (they are time stamped) It may indicate what wakes it up. (Applications/Utilities)

Are you using any bluetooth devices? I have a bluetooth Logitech mouse and I found the same thing happening. As it turned out just the vibration on my desk (not moving the mouse) was enough to cause the mouse to bring the machine out of sleep. Could that be it?

I was then thinking the same thing, but I couldnt really explain why it would go right back to sleep with that theory.