I'm not sure if this is related to the Vista Service Pack 1 Beta but I installed the SP1 beta recently and then within the next week or so I couldn't start IIS (W3SVC).  When I'd try to start W3SVC I'd get an error saying "The dependency service or group failed to start."  A little digging and I found out that the Windows Process Activation Service (WAS) wasn't started and that that was the dependency.

(A little side note: trying to search the internet on something called "was" is annoying because either the search service discards "was" as a noise word or I get a match on the past tense form of the verb 'to be'.  Mountains of useless results.)

When I tried to start WAS, I'd get an error saying "The Windows Process Activation Service service terminated with the following error: The system cannot find the file specified."  What made this extra fun to diagnose was that the "file specified" didn't show up in the error message.

Eventually, I found a page on technet that provided the answer.  The path that WAS was looking for was "c:inetpubtempappPools".  I re-created it and set the permissions as shown in the technet article and everything was working again.

-Ben