Are you trying to access your TFS installation over the web?  Microsoft today released a new Community Technology Preview of Visual Studio Team System Web Access.  Advances in this CTP include:

• Built against the TFS 2008 object model - In previous versions of Web Access you had to install Team Explorer 2005 on any machine you were installing Web Access on.  With this version, you will now be installing Team Explorer 2008 instead. 
• Custom control support - Support has been added for web based work item custom controls.  A folder with documentation and samples show you how to create them.
• Build queuing – The UI has been updated to support the new TFS 2008 feature of build queuing.  You can start new queued builds and view the build queue (in addition to the preexisting abilities - like viewing build details).
• Bug fixes & Performance improvements – Based on feedback, a number of bugs and performance enhancements have been included in this release.

This release (and the final 2008 release) can be used with either a TFS 2005 or a TFS 2008 server.  Against either server, you will need to install a TFS 2008 Team Explorer on the machine you install Web Access on.  Since TFS 2005 did not support build queuing, that functionality will not be available when this and future versions of Web Access are used with a 2005 server.

You can download VSTS Web Access here.