Windows 7/XP network nightmare

Here is the scenario:

We had an XP based workgroup, with specified directories shared between all. We replaced on of those machines with a Windows 7 Pro machine and had no problems joining the workgroup and having the same shares. We then replaced one of the remaining two XP machines with another Windows 7 Pro machine and that's when we started having problems. I have solved all of those problems sharing between the machines with one major exception - the last remaing XP machine gets access denied message when trying to access the shared directories on the newly added Windows 7 machine. However it gets access to the older Windows 7 machine no problem, and the two Windows 7 machines can access the XP machine no problem. It's curious that this XP machine successfully gets access to the older Windows 7 machine, but not the new one. I've checked and double checked the settings in the Network Sharing Centre of both the Windows 7 machines. I created a new user with the same name as the user on the XP machine on the problematic Windows 7 machine and assigned full permissions for that user (and at any rate the permissions on the folder we are trying to share have been set to full rights for 'Everyone') but still no luck.

I cannot understand why this XP machine can get access to shared directories on one Windows 7 machine and not the newer other one, and I have run out of things to try to resolve the situation.

Can you help?

Thanks

 

Anyone?

 

You could try checking windows security updates on the Win 7 machines to be sure they are the same .......just a guess tho.