Steam won't go online

Hi i've read that others also have this problem.

I just bought Killing floor, but i can only play the solo part.
This is the message i get when trying to go online:

"Steam must be running and you must have an active internet connection to access this"

My steam IS running, and my internet connection IS running! So why do i get this error?
(And no, its not my firewall blocking it...)

Second problem. The two characters pack: Outbreak & Nightfall DLC, is apparently not working. I guess this problem is related to the online issue.

I have sent a message to steam support, and are currently awaiting a reply.

How many others does actually have this problem?