I think the source of the crash has to do with a simultaneous kill while using the weapon you spawned with. When a person carrying a weapon he spawned with dies, the weapon gets removed, however the paintball has a pointer back to the weapon for use with the death messages. The problem occurs when the server tries to get the weapon name from, well, nothing. I've rewritten this using an ID system (paintballs have a weapon ID rather than a pointer back to the paintball gun) so it should stop the crashes in the next release.