I need urgent help!

When I start Garry’s mod on steam, it launches normally, then after 4-20 seconds, it crashes and gives this engine error :

                     SteamClient()->GetISteamFriends

I Dont know what to do, I love this mod, I love this community(well most of it,) and i want to keep playing. So, please Help.

Olazaika

[editline]07:01AM[/editline]

Oh, i forgot my Computer Specs :
AMD Athlon 64 3800+
1GB ram
Geforce 8600GT+
Windows XP

http://www.garry.tv/?p=1881