While my sister's 8300 is charging the screen turns on every 30 seconds or so. Basically, it will charge normally, but as soon as the Blackberry has a full charge the screen turns on by itself...then off after 30 seconds...then back on! If I turn it off manually it turns back on within 5 seconds and repeats the process. What is the deal here? Do I need to have this device replaced or is there something I can do?

Sounds defective to me. If with in the return period, I would ask for a replacement

same thing happens to mine... doesnt bother me thought but it does happen. When its charging it randomly turns on and then 10 sec later goes back off.... and when its fully charged it stays on all night ... doesnt bother me like i said because I put it upside down.

Hmm...none of what I have described happens until the phone has fully charged.