LARTC - Jun 2005 - ARP spoofing

Hi All,
I have a program that does ARP spoofing (not for hacking purposes!),
and I experienced occasional crashes in my switch (Cisco UBR7200).
Does anyone else had a similar problem? Maybe with other switches/routers?
Can this be the results of two machines trying to register the same
IP? Send invalid ARP packets?

Thanks,

Yuval.