Cron run kills Chat?

I have set up cron to be be run every hour, minute past. Now this seemed to crash the whole site, if people are in chat when cron runs. The site was completely unavailable for some minutes, and then everything was ok, like nothing happened.

I (krhmmm) managed to screw the screengrab I took from the mysql error that appeared in the chat window, but it looked like lost connection to me.

Br,

Jon Grönvall