Did you try logging in at another workstation? If that works, and you have a static IP address you are toast. If you have a dynamic address you can try to release and renew the address from the command line.
It's been a while but I *think* it is:
/ipconfig release
/ipconfig renew
USAGE:
ipconfig [/? | /all | /release [adapter] | /renew [adapter]
| /flushdns | /registerdns
| /showclassid adapter
| /setclassid adapter [classidtoset] ]
adapter Full name or pattern with '*' and '?' to 'match',
* matches any character, ? matches one character.
Options
/? Display this help message.
/all Display full configuration information.
/release Release the IP address for the specified adapter.
/renew Renew the IP address for the specified adapter.
/flushdns Purges the DNS Resolver cache.
/registerdns Refreshes all DHCP leases and re-registers DNS names
/displaydns Display the contents of the DNS Resolver Cache.
/showclassid Displays all the dhcp class IDs allowed for adapter.
/setclassid Modifies the dhcp class id.
USAGE:
ipconfig [/? | /all | /release [adapter] | /renew [adapter]
| /flushdns | /registerdns
| /showclassid adapter
| /setclassid adapter [classidtoset] ]
adapter Full name or pattern with '*' and '?' to 'match',
* matches any character, ? matches one character.
Options
/? Display this help message.
/all Display full configuration information.
/release Release the IP address for the specified adapter.
/renew Renew the IP address for the specified adapter.
/flushdns Purges the DNS Resolver cache.
/registerdns Refreshes all DHCP leases and re-registers DNS names
/displaydns Display the contents of the DNS Resolver Cache.
/showclassid Displays all the dhcp class IDs allowed for adapter.
/setclassid Modifies the dhcp class id.