Network Access Denied

[William Martinez]

I have a small office network with 5 computers, all in a
workgroup (no Domain).
Three of them can connect to Internet using a modem, so I
installed the MS AS only on those 3. After that, they all
continue to see each other in the network, but the 3 that
have the AS started rejecting connections through My
Network Places (access to the machine is denied, as if you
have no authorization).
The two machines that don't have AS, accepts the conection.
The funny thing is that the already shared and connected
printers do print, but now no one is able to access the
shared folders on those machines.
I deinstalled MSAS, runned the fix that appears on other
posts and nothing helps. In fact, I see that is not TCP
stack problem since the other machines and the printers
work fine, it is just a rejection of the machine or the
user, like if no one has permission to access the folders.
And I checked all the security settings and policies, all
are the same than the two machines that work.
Help please, don't tell me the solution is to reinstall
everything!