>>Very simply...
>>
>>

>>WORKSTATION <--------------->|
>>                             | HUB
>>     SERVER <--------------->|
>>

>>
>>That's way I don't understand that they can't see each other anymore.
>>
>>
>>>Ok using a hub & not a router kinda changes things...
>>>
>>>I don't quite understand you're configuration....
>>>
>>>You have how many machines connected to what?
>
>It seems your computers are trying to get IP addresses dynamically, through DHCP. This seems unnecessary for such a simple setup.
>
>Instead of automatically getting an IP address, try giving each machine a static IP address. It is preferable to use private addresses.
>
>Thus, the server might have the address 10.0.0.1, and the workstation, 10.0.0.2 Subnet mask, in both cases, might be 255.255.255.0.

That's not a bad idea either.