Welcome to the SeeMeCNC Community

I just replaced my printing computer due to a failure on the old one. It's a new Dell minitower, plenty of horsepower for the job. My first build stopped after about a half hour, the hot end just froze on the part, and Mattercontrol showed a communication error. It appears that the Rostock Max V2 keeps the heats going when this occurs. I cleaned everything up and shut down/restarted Mattercontrol, started over (same part but different build orientation). Same thing happened, after maybe a half hour. Where do I start to figure this one out?

The best suggestion most would give is to print off the SD-Card only, although I understand the convenience of using the USB. I use USB solely unless I'm printing a part overnight, then I use the SD-Card.

I would start by disabling the power saving option in the device manager. Switch the USB cable for a different one. Use a USB 3.0 port if you have one available. Use a separate powered USB hub if you don't have 3.0 on the motherboard.

Remove the side panels to verify that the Rambo isn't overheating by using a fan blowing over the board.

Also, you can disable XHCI in your BIOS if it has that option.

I think KAS is on the right track with the power saving option. You said it's a new computer; did you forget to tell it not to go to sleep when it's idle?

I agree with KAS. I had the same problem with my iMac and communication loss when the iMac went to sleep.