Not all users can access the network--Need Help!

We have three networked computers. All three share files. On one of the computers there are 5 user profiles and all are set as administrators. 2 of the 5 user profiles have access to all computers and the other 3 user profiles can access one of the computer's shared files but not the other computer's shared files.

We have checked all the settings to ensure that all user profiles are the same and they appear to be. Also have checked the permissions on the computer that the 3 profiles are unable to access. The permissions appear to be set at full access to all.

I suspect that it is a permissions issue on the computer that 3 of the 5 can't access. Just can't figure out why 2 user profiles have access and the remainder do not!?

Any help or suggestions would be appreciated.

All three are running Windows 7 and configured as a Homegroup. Microsoft security essentials, malwarebytes.

Please note that two of the user profiles CAN view shared files and three others on the same computer cannont even though all settings are the same -- all administrators, etc.

No, and I'll apologize up front if I am using incorrect terminologies but here is the situation. There are three computers in our office and each shares files with the others. There is only one user profile on two of the computers. The third is a centralized computer on which each of my five employees can log in on their user profile to access files from the other two. Two of the user profiles can see the other two computers and the other three receive a permissions message when attempting to see shared files. Basically "you do not have permission to access this file--see the system administrator..." or something to that affect. All of the user profiles are set as administrators and when I check the permissions area of the network, each of the files that are shared are marked as "everybody" has rights.

For what its worth, I spent an hour and a half with Microsoft support and the first level support could not figure out the issue. They elevated it and I was supposed to have received a call back but so far have not. They now say it will be tomorrow but, in the meantime, I've got guys losing work.
Any help/guidance would be appreciated.