Hello, I know this is an older thread but maybe someone will get some help from it. This problem PLAGUED me for a week and I found the cause. I think I did anyway, I'm not preaching gospel, just letting you all know what worked for me.
I have 3 Curve 8530's all running the same operating systems. Mine and my son's connect to any of our PC's just fine and do what there supposed to. When I plug my wife's in it immediately reboots, a hard reboot just like a battery pull. They all have various software running but no reason just hers should do that????
What didn't work: resets, reboots, battery pulls, using a different USB cord, connecting to a different PC, swapping batteries, swapping SD cards, default restore, OS upgrade, calling tech support, swearing, begging, or hammer punching my desk. Not a dang thing worked to fix the problem....
Then I noticed her BB Messenger App wasn't running in the background. Even if you never use BB chat this application is used to send push data to your phone and for other communication operations. As far as I know you must have this app running all the time for proper operation. Check this by holding down the BB menu key for a second, this shows a list of apps currently running. Scroll through the apps that pop up and look for the BlackBerry symbol inside a chat bubble, if this app is missing from the list I bet its your problem. Somehow the BB messenger service has been uninstalled from the core app list.
None of the solutions mentioned above fix this problem, even an OTA upgrade wont solve it because this is not a file that is re-installed by default. No other thread I read had a solution nor did Tech support, that's why I'm putting this (sorry) honorably long post up!!
The Fix!!
If you haven't upgraded to the newest software for your handset go to
Options>Advanced Options>Wireless Update
When the handset finds an available update go ahead and install it, but look through the options, DON'T JUST DO A DEFAULT INSTALL!! Aside from the language menu open every sub-menu (the + sign next to the folder) and make sure they are checked. It will be a heavier download but some core apps are not bundled with the "default install" in order to make the download smaller, hence the reason why an upgrade won't fix your problem!! After your lengthy download and install is complete your problem should be solved!! *Note: If you already installed the new 5.0 OS then just reset your BB to the original factory settings and follow the steps above.
I hope this helps someone because I am pretty good with Google and I couldn't find this answer anywhere, nor could tech support. Good luck all....