Judging from when that G-line kicks in, it seems to be based on either your hostname or ident - doesn't look like there was time for a portscan. Also, it gives the reason as "trojan clients" (plural), not "you are/have a trojan". So... a couple of possibilities:
It's possible that the network has had so much trouble with trojans from your ISP that they have simply banned the whole company - in which case you suffer even though it's not your fault.
IF this is the case, your choices are basically to change network, change ISP or wait until the situation is resolved. Not sure about Quakenet specifically, but some networks do publish the names of ISP's that they have banned for being unco-operative in dealing with problems like trojans.
Alternatively, it could be that your ident matches a pattern used by certain trojans. Try changing your ident, and see if that makes a difference.
In any event, ALSO run a good, up-to-date antivirus (or at the very least run an online one), and for extra surety, run an anti-trojan package like PestPatrol, too.
Good luck!
PastMaster
