Until Meg gets back to answer...I'll do our standard support dance.
Use FastDL? Updated gmod server cache?
Playing in SP you say? Screenie of update you show...that for SP or Dedi?
If Dedi...did you update local game paths too?
If SP...wait, where are you getting the errors? You mention both dedi and SP?
Is this happening in a single player game, client hosted game, or dedicated server game?
And, second finally, you shut down all games/servers while updating, ran each once, then shutdown, and reuploaded cache, then restarted where applicable?
And, then finally, you're running this in sandbox, with no other mods that say they've updated for the beta but may not havef or latest beta update?