port 110 blocked by my PC

Somewhere in my win2k PC port 110 is being blocked. I can't use port
110 to reach my mail server over the internet. It is not my hardware
firewall since I ran the PC straight into the DSL modem and the port
was still blocked. My ISP does not port block. Using a different PC
connected to the same DSL modem, I was able to reach port 110 at my
mail server, so it has to be something on this particular PC.
ZoneAlarm is installed but turned off. The same goes for Norton
Antivirus. I can telnet into port 25 with no problem.

Running sysinternal.com tdimon, I get
40.59238457 hypertrm.exe:284 817E2AC8 TDI_CONNECT TCP:0.0.0.0:1663 XX.XXX.XX.X:110 CONNECTION_REFUSED-293
where my mail server is X'd out by me just in case the info is useful
to hackers.