Bermuda triangle coughs up requests hours later

I have a problem whereby a request is being sent from a browser and received by the server, which is good, but then the same request is being received by the server again anywhere between a few minutes and several hours later.

I have also had one case of a request being received 3 times. It only happens intermittently, maybe 1 in 3000 requests. I have client side javascript checking that the button is only pressed once and I have included a request parameter that shows what time the button was pressed in hours, minutes and milliseconds. This timestamp shows that the button was pressed only once for each duplicate request (or multiple times within the same millisecond).

The webserver is weblogic 5.1.

Beats me!