So you have configured your Windows Server 2008 Terminal Server with:
Server Manager >> “Configure Remote Desktop” >> Systems Properties >> “Remote Desktop”
as “Allow connections from computers running any version of one of Remote Desktop (Less secure)”
And your XP clients get a quick RDP connection but Vista clients hang for a long time and sometimes connect and sometimes don’t, then it’s a firewall issue. (Clarification: this post does NOT apply to a TS Gateway.)
Not a firewall issue for traffic to the Terminal Server (TS) but a connection between the TS and your Domain Controller (DC)!
If your design includes a firewall between your TS and DC, first make sure you have the basic rules configured.
Then make sure you’re allowing outbound TCP port 49157 between TS and DC. It is a port used by svchost.exe and lsass.exe during authentication.
Presto! The connections from your Vista clients will be lightning fast.
Corner Edge likes their Vista lighting fast.