I am afraid this will only be comfort and not help.
But I doubt if it is the browser.
I had the same problem on a remote jboss 3.2.6 server being hosted by eApps -- A ghost servlet I could not kill.
Stopping the server, removing all deployed apps, clearing all temp versions, restarting with nothing deployed (to see that the servlet did not respond -- it didn't), then redeploying a modified servlet and restarting == old servlet returned from somewhere? and modified did not take.
To eliminate the browser, I wrote a
java client that made the GET http call to the servlet, and it received the output from the "ghost" servlet instead of the current one also.
We (me and the eApps tech staff) never were able to kill that ghost, so until I moved to jboss 4.0 I could never use a Servlet with the ghost's name again. Other servlets worked and updated fine.
Hope you have better luck.