Net send don't work and computers are no possible to open

[girts]

Hello,

There is problem with some computers which are in Domain and using Group
Policy from Domain controller. Net send don't send to these computers message
and computers cannot be opened in Entire Network > Microsoft Windows Network.
When I had turned Firewall on these computers then Net send works and there
is possible to open computers under Entire Network > Microsoft Windows
Network.
What to check, where is problem and what is need to do?

Regards,
Girts

 

[girts]

Don't read this, read recent post. This was written again because newsgroup
site show error and don't write my info on server and I writed the same again.