Could not load type 'Microsoft.TeamFoundation.workitemTracking.Client.WorkItemTypeDeniedOrNotExistException

So this came up to me every time I tried to view a work item in TFS 2008 on Visual Studio 2008 on a fresh installation on vista. 

apparently some dlls don't get registered properly when installing SP1 sometimes. I'm not sure if it's a vista thing or if it's just random, but in any case the solution is simple: reinstall VS SP1 and it's happy days! :)