game von't start

i basicly said it all in the titel!
when i click the game steam says that garry’s mod is starting in thet little black box and then the advertising that pops up when i close the game comes up
it worked yesterday and i have not made any changes!

Can somone please help?
Sorry for bad spelling, Im Norwegan

http://www.facepunch.com/showthread.php?t=1234220

its vorking now since garry sent the update to steam