Unable to access any site with a active vpn connetion

hello can any one help me to solve my issue
iam using an datacard for a vpn connection iam able to browse any site with out vpn connection and after i connect to vpn iam unable to access any site in IE8 but i can access the same in mozilla and if i disconnect vpn iam able to do the same in ie also ?

please suggest what would be the issue.