Wirelessly posted (8700g: BlackBerry8800/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)
1-I doubt anyone has any statistics about how often yopur issue occurs.
2- You need to read the
http://www.blackberryfaq.com/index.php/Main_Page for info about upgrading your OS and wiping with Jl_cmdr utility.
Good luck.