I am using the offical release of DM 4.5 with 8820 (4.5 OS), I found everytime I plug the usb cable, I will get an error message, please see my attachment.

In this case, i am not allowed to sync with outlook but i can still open application loader, i also tried the DM 4.6 beta, same issue.

I also found if you re-insert the sim card, it may work for a while, then failed again.

Does anyone have any idea of it?

Many have this problem with DM 4.5 and 6. Some don't. These versions are buggy. Most just go back to DM 4.2.

just drop back to 4.2 sp2 and see if that works.

Does DM4.2 work with 4.5 OS?

I dont see why it wouldnt.