Why does my EVO Android phone screen keep turning on?
First, killing background processes will do nothing; they'll just be restarted.  Instead, focus on apps.  You could use an app like Titanium Backup (requiees root) to "freeze" an app, and see if the problem stops.  If it does you know what app is the problem.  Then uninstall it, or turn off background sync for it or something if that might be the problem.  TB can uninstall system apps, but be careful which ones.

I had this problem when I had SipDroid installed -- every time its connection dropped and came back up, it would turn on the screen.