There are bugs that keep you up at night. This was one of them. Our web site at Avery.com has been getting a flood of error reports in the JRun log. There were no bug reports from users, though, and nothing that I did on my test machine could duplicate the error reports i was seeing on the production site.
Coworker Brad found the problem before I logged in this morning. It was specific to the Firefox browser. It seems that under certain conditions, Firefox will fire off a GET request with no parameters following a valid POST. The users got their response from the POST request, and the GET fell into the error log.
I rewrote the code to ignore the bad GET requests if the UserAgent is Firefox. That should fix it.