An IP conflict won't cause watchdog resets.
I've been getting a few of them on OS7100's lateley.

D/C from customers network and system is fine, re-connect and it dies.

1 customers IT guy and I came to the same conclusion, it would be nice to figure out what was causing it, but the time/cost involved isn't worth it, so he was going to put a ethernet router between the system and the switch, havn't had an issue since