I have had loads of problems with steam, still do actualy which why I am mapping for hl1, but never mind. here is my advise from my own experience
1. Don't use the website for help - it is rubbish
2. If you send emails moaning they will take ages to reply and will basiclly tell you to defrag you pc, reinstall steam ect
3. I found the best way to get it to work, is every time it has to update, disable every firewall you have, including windows. Although they dont block steam, it still cant update with them on I found.
Hope this helps.