Since I had a power outage at the weekend, I'm getting

Arp address mismatch - Ethernet destination address doesn't match ARP target adress

error messages in my syslog on my 2860 at least once a minute. The message is really unhelpful since it doesn't tell me what device is causing the problem, and I don't really understand what could be causing it. I've seen some comments with other arp errors on using wireshark, but since I don't know anything about the source of the error, I'd have to capture everything from all devices and try and spot of cause. Anyone got any ideas on how I can try and discover the cause of the problem?