Do you think the plug got over tightened or was threaded wrong? Best thing to do is drain it again and get a new plug to be on the safe side.

I always use http://www.hylomar-usa.com/ on all my threads and gaskets. Great stuff and it will make the plugs come off easier the next time.

__________________
2001 X5 3.0i "Dodi"
1993 Range Rover County LWB (71,600 miles) "Bertha"
1991 Range Rover parting out