Power failure

I have a small office network that I manage. I have the computers log into a server every morning so they can access there files. Everything was working fine friday when I left. We had some storms and a power failure over the weekend. I come in this morning and everything seems to be working fine, but two of the computers on the network can't connect. They don't even see the rest of the computers in the work group. Nothing has changed since friday. All that happened was we lost power. Which the two computers were off when that happened. So i'm not sure how I can no longer recognize the servers there but the rest of the computers on my network can. Any ideas?