Networking disabled

[afip]

Hi all,

I'm new to GNU/linux and my box at work has Ubuntu Lucid 10.04 LTS with 
Gnome desktop. Everything was working just fine up to yesterday, when I had 
to lend my pc to a co-worker (with an unprivileged user ofcourse), and when 
I showed up this morning I noticed the pc hadn't been shutdown properly (it 
was still on, but locked-up), so I had to do a hard reset.

Then, when the gui came up I noticed there was not network connection (only 
the Local Loopback interface was up). NetworkManager at the top panel says 
that networking is disabled (I'm writing this mail from a win pc, 
unfortunately!).

What do I need to do to re-enable networking? What other information do I 
need to post here? I don't know where to start from. Any help would be 
greatly appreciated. TIA,

PS: I have no internet access since I'm behind a proxy at work, so I only 
have intranet access, hence I couldn't do any googling.
--
afip