Originally Posted by DJMONDY
The only thing i can suggest is while in offline mode to right click on hl2 in the steam list and untick keep this game updated (i think thats what it says).
This would also work if you buy the game and you would not have to wait for updates you should just be able to play straight away.
Hope this helps
I have done this (it was already selected) but doesn't make a bit of difference...