Firewall issues since the SWEN virus

Hi,
I have just finished cleaning out our system witht the SWEN virus.I was also experiencing problems with our Watchguard firewall as it was getting flooded with NAT pools exhausted. I thought that this problem would go away but I am still having issues with the firewall. I am running SBS with Exchange 2002. The machine that was infected is offline and all other workstations have been scanned.
Please help.

Mil