I have seen a few older switches, that when they were subjected to things like ettercap, or even things like NMAP or Nessus, essentially lose everything (basically like a factory reset, if you were lucky, if not, it had nothing, no IOS). I would say if you have newer equipment the chances are very remote that something non-recoverable would happen, with older equipment I would say that the chances are still remote, but more likely than with newer equipment.

I would be more worried about the 3COM, I have seen nmap scans torch their routers, corebuilders, and Superstacks...

/nebulus