I have found that the /3GB switch doesn't really do any good unless you have 4GB of memory in the machine.
With 3GB in your machines, you don't even have 2GB of memory for Pro/E since the OS takes 1.1GB and the graphics card takes some more of what is left.
Try upgrading 1 machine to 4GB and utilize the /3GB switch with /USERVA=1100.
You did not say which OS you are running, I am guessing Win XP.
Wildfire 5 does seem to use more memory than WF3 did.
The simplified rep usage is a good way to help manage limited memory resources.
Ben H. Loosli