[jsimmons]

Hardware:
AMD dual core CPU
4GB DDR2 RAM (soon to be 8GB)
NVidia GTX1050
Connected to home theater receiver (HDMI)

Monitor:
75-inch Sony 4k TV (about a year old) connected via a home theater receiver (HDMI)

Software:
Ubuntu 18.04 with screen locking disabled, no screen saver, plain color background, and auto-updates turned off
Kodi 17.6 (as installed, with no additional add-ons, UPnP is disabled)
Proprietary drivers for the NVidia card

Media:
Library of over 1000 movies stored on a separate server (six 2-3 TB drives formatted to EXT4)

Network:
All machines are hard-wired with Cat6 connected through GB switches.

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At about the two-hour mark, the entire machine freezes up, and I have to reboot. The only time this machine freezes up is when I'm watching a video through Kodi.  I have not yet enabled logging, but I will when I get home from work this evening. In the mean time, I thought I'd put this out there on the off chance that someone has any immediate ideas that might help.

[Klojum]

To receive meaningful assistance you will need to provide a full debug log.

The instructions are here... debug log (wiki)

If you are using the Basic Method, then ensure the following is applied...
1.Enable debugging in Settings>System Settings>Logging,
2.Restart Kodi
3.Replicate the problem.
4.Upload the log to Kodi Paste Site manually or use the Kodi Logfile Uploader. (wiki) With either method post the link to the log back here.

If you are using the Advanced Method ensure you have correctly created and applied the advancedsettings.xml file (wiki)

In both instances, you should see the word DEBUG throughout the log.

Note: Full logs only. No partial or redacted logs
Do NOT post your logs directly into the forum. Use the Kodi Paste Site. Post the link to your pasted log in the forum