I uninstalled my web accelerator software, and BAM....problem solved. Just to be sure I reinstalled and the problem returned. When I uninstalled again, the problem was again gone.
Apparently the software leaves ports open to speed up the process. So it is a case of what do you want? Security or Speed.
I don't know if this is your problem, but it was the answer to mine.
Hope this helps.
raisinh2k4