Required connectivity to use Remote Web Workplace - Port 4125 is important!
Thanks to John Joyner (Essentials TAP customer) for pointing out this great article that details connectivity requirements when using Remote Web Workplace - especially on a computer that's running the ISA firewall.
ISA Server prevents connection to a remote desktop when you connect through Remote Web Workplace on a Windows Small Business Server 2003-based computer
http://support.microsoft.com/default.aspx/kb/828053
