Well, I'm running the phone on default stock speed and as I've said - a 3GB file, which is .avi (Xvid), has a resolution of 720x400, videobitrate of 3000 kb/s, 5.1 channel ac3 audio and audiobitrate 384kb/s, with subtitles, plays without lag and without any prior conversion without problems. So I think the problem is at your end somehow. Overclocking can in the long-run be a bad idea. But if you switch phones every 6 to 18 months, I guess it won't hurt.