Trouble transferring pc to pc over home network

trying to transfer files from computer A to Computer B. I get This error msg .

"Network error. There is a problem accessing \\fire\downloads. Make sure you are connected to the network and try again."

I am connected to the network and have full access. It will start the transfer and will get to different percentages complete then give the error. I Thought it was my router so I bought a new one. Trendnet dualband wireless n gigabit router. My pc's are dell inspiron 1525 with vista 32 premium, A custom pc running vista 64 ultimate and a gateway running vista 32 premium. The problem started happening every once in a while then got more and more frequent. Now I can't transfer anything. I have tried everything i know. Someone please help. My E-mail is gavit77@yahoo.com if you wish to communicate thru email.