I have flashed my SGS to 2.3.5 (XXJVS) from Froyo 2.2 a couple of months ago. I have started to notice something. After I lock the screen with the power key, the screen randomly turns on and off without interval. Its not a big deal but its quite annoying cuz I put the phone next to me when I sleep and you know... What could be the problem?

P.S: I am planning to flash ICS on it, is it worth it? If so, what is the most functional and stable ROM? [A link to a good guide would be appreciated] Thanks!