remote screen fails after upgradation

[H.S.Rai]

I upgraded from Ubuntu 7.04 (Feisty Fawn) to Ubuntu 7.10 (Gutsy
Gibbon). What I found now that other PC can not this computer's screen
login, using command like:

> X :0 -query upgradedPC

while earlier, it was working.

On upgraded PC, I checked, XDMCP, it is configured to accept
connection on UDP port 177. portmap is not showing this port open,
even after using firestarter to allow other PC, and opening port 177.

What could be the reason, and how I can access desktop (login screen)
of this upgraded PC from other PCs

-- 
H.S.Rai