In the past year or two I have noticed the same issues coming up again and again. Each of the issues have been resolved by deactivating or configuring the firewall component of the installed Anti Virus software.
I have noticed it mostly on McAfee and Symantic Anti Virus.
The issues that can be solved by deactivating or configuring your firewall are:
- No file share access to computer with firewall on it.
- No shared printer access.
- Cannot see some or all computers on the network.
- Cannot get to email server.
So if you ever have the above problems check the configuration of your firewall and make sure it is correct. Obviously I would recommend that you keep the firewall activated but you can deactivate it just to check that the firewall is the cause of your problems.
This saved me a lot of time. I hope it does the same for you.