2x Client (RDP issue?)

I just had deployed a untangle box as a router my local structure is Public networks - Untangle box - Local Clients

We are using a 2x client application as of now we have problem accessing it from the local clients but for the necessity of the application we had connected some computers directly to our public networks. i have already tried the following:

1. since the 2x client uses the gateway mode (using port 80) i had tried exempting it via packet filtering
2. tried exempting the domain that i was connecting to via web filter

and also we keep seeing DNS lookup failed dont know if it related
actually i am a newbie in networking

Thanks for the help