General mulitplayer problemo

[Atomic_Piggy]

Kk, so I've had loads of problems with my mulitpplayer games (specifically source) in the past, and now I'm gonna ask for help.
First, my mulitplayer for HL1 (TF:C, DoD, CS) worked fine for ages, then one day (couple of days ago actually) it happened. Whenever I try to join a game it comes up with "you have been discontteced client timed out while answering a challenege" then takes me back to menu.

On my Source (CS:S, DoD, The Ship, TF:2 -proboaly), it simply comes up with "Cannot contact master server" and whenever I try to create a game it says :"connection failed after 4 retrys".

Is this summat to do with my interent (BT Yahoo Broadband) or my security (Norton internet security) or do I just need to reinstall my games?
Please help. Please. Dudes.

 

[Atomic_Piggy]

Sorry for double post but can someone please help?

 

[Beerdude26]

Try deleting your Clientregistry.blob :
Exit Steam. Delete the clientregistry.blob in the main Steam folder and the platform.gcf file in the Steamapps folder. But make a backup of them first by copying them in another folder! Now restart Steam.

 

[bigburpco]

Mulitplayer problemo... Sounds great.

 

[Atomic_Piggy]

Its not there, I've only got Steamapps and all my HL1 Mods tehre. Nothing else.(and various readmes, uninstalls,exes. etc.)