I had the exact same problem with my Captivate which, at the time - I was running Serendipity 6.4. My accelerometer just STOPPED working quite randomly and for no good reason. I scoured forums and more forums and used MANY different sensor reading apps and other apps that would 'configure' the accelerometer/g-sensor.... the ONLY fix I discovered for my problem was a factory reset. I just reset my device & reflashed Serendipity and that took care of the problem. Of all the posts on all the forums I read - no one quite seemed to know WHAT exactly the problem was. I didn't think it was the ROM. But, the only way to restore it's functionality was to do a reset and use Titanium Backup to restore all of my apps (but NOT system data, just in case the problem was caused by any system data/settings) I am now running Serendipity VII with the Serendipity VII #3.0 kernel and my acclerometer works just fine now.