Thanks for the reply Mek.
Sorry for forgetting to specify my stuff. WinXP 32 bit. Netgear DG834G router. Avast AV, plus Malwarebytes Pro. I've always believed (rightly or wrongly) that my NAT router is a good firewall, so I only also have Windows firewall running.
I have tried your suggestion, disabling all Avast real time shields and turning off Windows firewall with no effect.
Should I try to remove all and any entry relating to Apex in Avast and WinFW and re-enter them?
Actually looking at my Apex system directory, the .exe was last changed at the end of May and it only stopped working a week or two ago.
The only PC issues I know I've had recently have been updating ATI graphics drivers... that was as unpleasant as always as my whole system is old and creaky, A7N8X motherboard, AthlonXP 2500+, 2.5 gb RAM, Radeon 9600XT video... etc.
But that doesn't seem to explain why uTorrent and CzDC should be happily working away while I can't connect to anyone with Apex (hub users can still connect to me with Apex)
So if anyone cares to have another shot in the dark, I'm wearing a luminous target on my head... thanks :)