You might encounter following error if you try to connect to Team Foundation Server 2008 from TFS 2010 Beta 1 even after clearing 'Path' Text Box

TF31001: Cannot connect to Team Foundation Server at <xyz>. The server returned the following error: The ServicePointManager does not support proxies with the https scheme.

Solution:

Run Command Prompt as Administrator and run following commands...

reg add hklm\SOFTWARE\Microsoft\VisualStudio\10.0\TeamFoundation\RequestSettings /v BypassProxyOnLocal /t REG_SZ /d False
reg add hklm\SOFTWARE\Microsoft\TeamFoundationServer\10.0\RequestSettings /v BypassProxyOnLocal /t REG_SZ /d False

Additionally on a 64-bit machine...

reg add hklm\SOFTWARE\Wow6432Node\Microsoft\TeamFoundationServer\10.0\RequestSettings /v BypassProxyOnLocal /t REG_SZ /d False
reg add hklm\SOFTWARE\Wow6432Node\Microsoft\VisualStudio\10.0\TeamFoundation\RequestSettings /v BypassProxyOnLocal /t REG_SZ /d False