I know a few people have had this issue, but I don't think it's ever been found out why it happens.
I will just be sitting there, full 3G, full bars, and all of a sudden drop 3G for no reason, and then it will just randomly reappear a couple minutes later. I know it's got nothing to do with signal, it almost seems as though it's a glitch in the system, because if you cause a reboot to the service (you can usually do this with a task manager by killing the hiddenmenu item, which will cause it to reboot that item, and also reboot the service... this will disconnect calls when you do it also, that's how i know it reboots the radio or something) or radio, then it comes back with 3G once again. There is zero reason why this happens from what i've seen, and it's completely random, i only have it happen once or so every other day.
I will just be sitting there, full 3G, full bars, and all of a sudden drop 3G for no reason, and then it will just randomly reappear a couple minutes later. I know it's got nothing to do with signal, it almost seems as though it's a glitch in the system, because if you cause a reboot to the service (you can usually do this with a task manager by killing the hiddenmenu item, which will cause it to reboot that item, and also reboot the service... this will disconnect calls when you do it also, that's how i know it reboots the radio or something) or radio, then it comes back with 3G once again. There is zero reason why this happens from what i've seen, and it's completely random, i only have it happen once or so every other day.