Sylvain, I know it sounds silly but you must have the same updates of the VE server and VE Pro etc. on both machines? The PC version might be a version ahead or behind the Mac it is very important that they are exactly the same.
Also if the Mac is your master DAW then change the IP address config around making your MAC 10.255.255.1 and the PC 10.255.255.2 it might help.
If your seeing the PC and user files on the Mac and the PC sees the Mac then it doesn't sound like a Network connection issue. check with the above thats all I can offer I wish you luck.