cannot get ping from my server!

Just i finished an office network using a server with windows server 2003 having no problems!
After a power failure i have some serius symptoms on my server.
The sturcture of the network is
router-server-switch-workstations
the promblems are:
even if i can see in the workgroup that i am the name of my server, i cannot get in and the most important is that i cannot even get ping,five days ago i could.

i have a service tha does not start during the boot and this is the Windows firewall/internet connection sharing(the requested resourse is in use)
when i try to start the service i get a message about ipnat.sys

are these two promblems connected what can i do??????