Although I bought a WiFi + 3G TAB, most of the time the TAB is running on WiFi without sim card. But once a while I might use it with my sim.
My sim seems to be working fine on my Sony Ericsson X1 and I've actually swap two different sims to the TAB and both are showing similar results.
As I know before the Gingerbread upgrade on Kies, there will be an additional icon (sim card icon) if the sim is not inserted. As for my case now, the icon is not shown with the phone software = unknown. Sometimes after a few reboot, the icon reappear and the phone software is shown correctly but still unable to register to the network (although the 'EasyAccess' services on the Maxis sim is shown in the TAB programs).
When I tried another sim and if the phone software is detected, at times the coverage bar will be shown for a few seconds (registering) and goes back to the (/) sign again and attempt a few more times before the phone reboots itself for a couple of times.
I doubt it is a problem with the sim, more towards the TAB, either on the software or the sim slot hardware.
I wonder if anyone else had the same problem or if I am the only ONE...