Intermittent no Internet access to some users over network with Local DNS/DHCP/PDC

[SFHR]

Hi there,

I have got a strange problem at my office network. Occassionally few users drop internet access while others have access. The environment is ML 350 G5 running Win 2003 Srvr acting as Domain Controller with DNS, DHCP and Exchange. Nework is we have CISCO ASA5500 Firewall before the Internet Router. All live IP Nating been done on firewall whereas behind firewall we have our own private IPs. Server and Firewall connected to 3COM backbone switch and rest all network is to same switch.  Clients are mix,some Win Xp, others Win 7.

This problem started a week ago, when some users reported of no internet, while others were able to access the internet. We initially checked ISA, removed ISA, problem still there. Reset all swtiches, routers, firewalls nothing worked.

To me its something wrong with PDC/Domain Server, causing the problem or is it firewall? Please help.

Regards,

SF Hussain   

[SFHR]

No Answer :(