I suggest trying multiple accounts and multiple characters in multiple zones, and trying them all with both EQW and without EQW. Makes notes of whether or not there's a pattern of characters, zones, accounts, classes, EQW use, or types of crashes (to character select, to desktop with error message, computer reboots/turns off)
This could be anything from a corrupted texture file to someone in the room adjacent to yours manually unplugging your modem.