Ubuntu Server 11.04 Samba file server stopped working - help needed to troubleshoot

Hi,

I am having some problems with my Ubuntu server. I am fairly new to Linux but have been getting along fine. I set up Server 11.04, running shared folders and drives via Samba. I also set up a static IP address for the server and added in to my network. It was all working fine, and I could access it from both OS X 10.6.7 and 10.6.8 machines and Windows XP machines. Files were transferring fine and all the shared folders/disks were showing up fine. Yesterday night the server dropped out for no reason - I couldn't see it on the network or re-establish a link up from any of the network computers although on checking Ubuntu the system showed no errors and was running fine.

I have tried restarting Samba, rebooting the whole system, checking the ifconfig and setting static IP addresses. I have no idea what to try next - nothing changed between the server working and not working and I can't access it from any of the network machines despite it running and showing up on the router's attached devices.

Any help would be much appreciated... I don't know what to do next.

Cheers,

Danny