I have had freezing problems with the PMDG B777,B737NGX and the B747-400.
My biggest problem has been with the B777.
About the time I started having Freezing (8 min freezing) I noticed that I lost my USB 3.0 ports.
I have 3 USB 3.0 ports and 3 USB 2.0 ports.
I have 1 USB keyboard,1 USB mouse,1 USB headset,1USB Saitek Cessna yoke,1 USB Saitek throttle quadrant,1Saitek USB rudder pedals and 1 saitek USB radio panel.
A total of 7 USB connections and I am down to 3 USB 2.0 ports.
In order to keep flying I connected all of my Saitek equipment to a 4 port external USB 2.0 hub.
This created a host of problems so I ordered a 4 port USB 2.0 PCI card (cheap).
While waiting for the USB 2.0 card to arrive I contacted my computer support group to see if i could recover USB 3.0 ports. the manufacturers support tech walked me through a BIOS reset default procedure and in less than 5 minutes I had my USB 3.0 ports back.
I then reconnected every thing back to the USB ports with the exception of the keyboard which remained on the external USB hub.A few days later the USB 4 port card arrived.
I installed the card in an empty PCI port and booted up and the card was recognized and drivers were installed by windows 7,With 10 USB ports available,all of my USB connectors has a port of its own
I have now flown the B777 over 20 hours without a freeze.
I have made it look like a USB port problem but I think it is really ganging Saitek equipment on a USB hub.
There is nothing wrong with the B777 or any other PMDG product and before I get a lot of know it all B.S. I just want to say this worked for me and I hope it works for you.