Win95 PC Suddenly won't connect with XP

I have a fairly simple file and printer sharing network with two wired pcs and and wireless laptop. In my workgroup, all pcs can be seen in my network neighborhood from all networked pcs. The first wired pc with most of my media is called MAIN, the other wired PC is called Radio, and the laptop is called Portable. One day out of nowhere one of the wired pcs (Radio) wouldn't connect to the other wired pc (MAIN) without a password. It did not ask for a login name, it just said "A password must be supplied to make this connection ", or something like that. I have never set up a password for my network at any time. My pc that im trying to connect to (MAIN) can connect to the laptop with no problem and vice versa and both MAIN and Portable can connect to Radio. Radio can even connect to Portable fine, just not to MAIN. I have tried admin, manager, and all other default passwords I can think of, current password on MAIN and all possible previous passwords, current password on Radio and all previous passwords, and STILL no avail. Why would it suddenly ask for a password? I have not changed any of the permissions on MAIN (double checked all my shared folders and "Everyone" still has read permissions) or on Radio. It has always been working fine until then. By the way, Radio is Running Windows 98 (regular not SE) and MAIN is running XP Pro. Please help.

 

Win98 or Win95? your Radio pc.

 

My Radio PC is Win98 (regular windows 98, not Win98 SE), my MAIN PC is WinXP Pro SP2.