My guess is that somehow the dude has been screwed up. It happened to me twice during the many dude 3.0rcX upgrades that I went through. How it is caused, I do not know - maybe I left an old dude running, maybe Windows just broke the dude, maybe something went wrong when I made Dude a service by ticking the box.
My fix was basically reinstall the Dude
1) Shut down Dude
2) Use Task Manager to make sure all dude.exe are gone
3)
Copy the "data" directory (usually c:\Program Files\Dude\Data) somewhere else
4) Uninstall Dude
5) Find anything left under c:\program files\Dude and delete it. Make sure no other dude.exe can be found on Hard Disk.
6) Check Dude windows service is gone
7) Reinstall Dude and set it up as a windows service and test (add a device, check is working, etc)
Stop Dude client and service again (making sure all dude.exe are gone using Task Manager)
9)
Copy*the contents of your backed up data directory back into c:\Program Files\Dude\data
10) Start Dude service - should be 2x dude.exe at this point, both running as SYSTEM, one using CPU, one not.
11) Run Dude client and connect to service - should be 3x dude.exe as this point 2x SYSTEM; 1x ITTeam
12) Hopefully everything is running well now, and the CPU using SYSTEM dude.exe is not growing.
*Note: Copy data directory. Best to keep a copy in case of a screwup.
I have ~70 devices and about ~700 monitors. My Dude Server (running 3.4; and 3.2 before that) has sat on 50% memory used for months. The only change occurs when I restart the server or upgrade Dude.