Windows 7 - Win7 asking for "Enter Network Password" when trying access

OK. I'm ready to pull out what's left of the hair on my head. I have a customer with 2 Windows 7 Professional machines on the same network we'll call them System1 and System2. System1 can see system2 ok but when we try to access system1 from system2 I get the "Enter Network Password" popup. Now the strange thing is that sometimes it works. If I futz around with it enough it will start working but eventually it comes up with this error again. I've tried everything I know and followed numerous posts on how to rectify the issue but nothing seems to work. I have the same username and password on both machines and I have "Turn off password protected sharing" selected on both machines. Everything I try has no effect. I need help..... Please........

If you are using homegroup, it uses IPv6 and has known issues with some legacy systems. You can keep what hair you have left by enabling a workgroup (IPv4 instead) and it wont require a password.

Thanks for the suggestion but I am using a IP4V with workgroup and both machines are Windows 7 Pro.

Workgroup prompting for a network password? I assume that is a change you/he made right?

I have it set up as share without network password in the network configuration area. I have windows managing the connection. Each system does have a username and password but they are the same. System1 can see system2 without any issues but system2 gets the "enter network password" when it tries to access system1. Both systems are setup identically. I've been working on this issue for 3 days now and can't find a resolution. I've followed numerous threads about the issue but non of them solve the problem. I think I might just reinstall Windows 7 on system1 and see if that helps.

Any difference in the Group permissions on the 2 machines? Are you using the full path for username and password (ie machine1\username\password, machine 2\username\password)?