Forefront TMG 2010 Blocking Internet Connectivity on the LAN

After migrating to Forefront TMG 2010, it ran smoothly over the weekend without a problem, on Monday, around midday, I got an error in the alert “Concurrent TCP Connections from one IP Address Limit Exceeded”. Both my DNS servers had been blocked in this alert and as a result there was no name resolution and this no internet connectivity for my whole office. I would also got this error on ISA 2006, but it would not block internet connectivity like in the case of Forefront. I have also (in both firewalls) put both my internal DNS servers in the IP Exceptions list of the Flood Mitigation settings so as to allow the highest threshold of concurrent TCP connections allowed. The server on which I installed Forefront was different from the one running ISA, and it was also fairly new and so I don’t think there is an issue with the NICs. Kindly advise what I can do to resolve this problem