Depending on the slots the game uses much CPU.
More info: http://forums.tripwireinteractive.com/showthread.php?t=57434
More info was sent on the mailinglist.
Thanks for the feedback. I will test it again.
Had max players 32 in the commandline, and changed it to 64. In the server browser it indicated 64 slots. Maybe I had to wait some longer to see if it disables.
Does it start in console mode? If not make sure Microsoft Visual C++ 2010 Redistributable Package is installed.
http://www.microsoft.com/downloads/en/details.aspx?FamilyID=a7b7a05e-6de6-4d3a-a423-37bf0912db84