[CentOS] Networking just stopped working

Hi all,

I have a box with a quad port Netxen NIC running Centos 5. All four 
interfaces are slaves of bond0 and bond0 is used by two vlan interfaces.

All was working just fine until just recently when everything just 
stopped working. ethtool reports all the individual interfaces are just 
fine. The switch is not complaining either. But I cannot ping anywhere 
not can others 'see' the box. Any ideas?

I have turned off iptables, rebooted the switches but still the thing 
won't work.

Christopher