... it might be that you opened a project/solution from a network share which is no longer available, or that is slow to refresh etc... I had this problem myself with Visual Studio .NET 2003 (not Visual Studio 2005 so far, so I'm not sure if this is also affected or not), and took a while to figure out what the problem was.
Procmon and some patience to go through the log pointed me to an interesting registry key: HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\7.1\ProjectMRUList (the same key exists for VS 2005, but it's under *VisualStudio\8.0\ProjectMRUList). This key contains the path of the last 20 solutions I opened/created; what's interesting is that by default Visual Studio does not show all the recent solutions opened (in File menu or in the Start Page) but just the last 6 (I usually change this value to 10), but despite that it reads all the values and (I guess) verify if the solution is still available, thus the delay...
To solve my problem I simply deleted the values pointing to a solution from a network share et voilà, Visual Studio was loading at the usual (reasonable) speed.