W32.almanahe.B!.inf

[DTx]

I have recently found that my work network is infected with the W32.almanahe.B!.inf Virus/Worm/Trojan?

Avast scanning does not pick up the threat, however Symantec Server Protection keeps finding and quarantining the files infected.
After updating norton corporate, it says the files could not be processed at this time.

My question is, how can i remove this infection from my network, or how could i stop it from spreading and causing further damage.
I use Avast 4.8 Pro and it is fully updated daily. Still it does not recognise that there is an infection.

Another problem is W32.sality.EU which avast does remove, however it keeps returning to my network.

What tools are available to find and safely remove these infections?
Please help!! I have had to do alot of reinstalling of programs, and formating of machines already, this threat will not go away!

[Eddy]

Shutdown the network, both external connections as well as local connections.
Clean the server, update the server software (if needed, patches, updates etc)
Protect the server.
Run a remote scan on ALL clients from the server.
Clean each and everyone of them.
Update ALL software on the client"s.
Protect the client's properly.
Have the client's automaticly scan ALL removable media on insert/connect)