OK, I have it narrowed down for the AppArcServerThread issue. I believe it is linked to specific applications being installed onto the QD. I have found that if I have Salling Clicker 2.02 or GoBoy 1.4 (only two I have found so far, there are probably more out there) installed on either the main memory or the MMC card, it will cause this error to show up. It looks like some sort of OS/application incompatibility is causing this. A good way to test this is to install the application and then go to Menu->Tools->Memory->Options->"Backup device mem" If the system backups up OK, then it will work with iSync. If not, you will have to narrow it down to which application is causing the problem. When you have an incompatible application installed and start a backup, the backup application will complain with the "AppArcServerThread" error. The backup (though in a rather slow fashion) will still complete its write to the MMC card. When the backup completes, the backup application will also complain that one or more files could not be backed up. I can reproduce this on my N-Gage QD with both Salling Clicker and GoBoy. I am sure there are other applications that have this sort of incompatibility also. If you do not do phone backups or use iSync, this incompatibility will not affect you. It makes sense now why taking out the MMC card would make the difference earlier. iSync worked because I had Switcher installed on the MMC card. When I took it out, the QD did not see the incompatible app anymore. This is a weird type of bug.