I just experienced the same problem but yours may be different. Turns out, the cable I bought at Radio Shack as a "crossover cable" was in actuality a "straight thru cable". I wouldn't have been able to know it for sure without the help of this site and the "How to" on "making your own cable". It was a lifesaver. So, you may want to check your cable to be sure you are using the right cable.
Once I connected the "crossover cable" it showed the two computers on the network and I was able to access them just fine.