Networking dead on my 2k3 DC??

when attempting to access a share using a UNC path I get this error: ‘No network provider accepted the given network path’
This is my DC and it runs DHCP and DNS. Those work fine exept I cant add new computers to the domain and drive mappings are failing!
I’ve tried various things like FSC /scannow, a script i found to fix it and just ran the windows repair utility on it.
Any ideas?
Any way to back up DNS and DHCP incase a format is necessary?