Playback in Premiere freezing

Premiere is freezing and then the playback will go black and I can't do anything.  I can hear the audio but I can't see anything.  If I wait about an hour, then it will have unfrozen and I can edit for another 5 minutes or so before it happens again. I have tried the following:

1. Resetting the preferences (by holding alt as Premiere starts up)

2. Emptying my media cache

3. Relocating RAM to Premiere's performance

4. Updating Premiere

5. Cleaning over 600 GB of storage on my computer's hard drive

6. Contacting Adobe Support (to no avail)

7. Previewing at 1/4 and 1/8 the quality of playback

Please help