BleepingComputer.com: Server won't share files

Okay, here is the situation. This is at a small business with five networked (not wireless) computers including the server. All of a sudden all of the computers (besides the server, obviously) can't access our main file we use all the time. It says can't find network path. Also, Peachtree Accounting is on the server and two of the others, and we can't get to that either. It says we may not have permission. So I tried to investigate and everything seems to be correct on the surface. I don't know very much at all about computers, but I tried to see if there was a firewall or Norton blocking the others, if the connection was good, what computers were listed, all that and everything was fine as far as I could tell. We finally shut them all down, started them up and could get into the shared file.

Peachtree still did not work and said that we might have to reinstall, so we did and everything worked! Then one hour later nothing did. What is going on here? I have no ideas, we don't have any IT people, I just happened to know the most, which is basically nothing. Any ideas would be greatly appreciated!!!!