Mac Mini, Yosemite reboot loop (** GPU Hardware VM is disabled)

I have a mid-2011 Mac Mini that has started to reboot spontaneously. I have ruled out hard drive and replaced RAM, but this is still happening. After several of these, the machine gets stuck in a reboot loop, from which it doesn't recover. I managed to get video of it in verbose mode, and the last line is:

** GPU Hardware VM is disabled (multispace: disabled, page table updates with DMA: disabled)

I ran Linc's script, and here is the full output:

Boot Mode: Normal

System diagnostics:

com.apple.AmbientDisplayAgent 2014-12-04-061937 crash

User diagnostics:

fontd 2014-12-03-185502 crash

fontd 2014-12-03-200331 crash

Kernel messages:

Dec 8 17:18:44 BUG in process suhelperd[179]: over-released legacy external boost assertions (0 total, 0 external, 0 legacy-external)

Dec 8 18:43:20 ** GPU Hardware VM is disabled (multispace: disabled, page table updates with DMA: disabled)

Dec 8 18:43:21 Previous shutdown cause: -128

Dec 8 18:43:26 BUG in process suhelperd[185]: over-released legacy external boost assertions (1 total, 1 external, 0 legacy-external)

Dec 8 18:44:10 BUG in process suhelperd[185]: over-released legacy external boost assertions (0 total, 0 external, 0 legacy-external)

Dec 8 19:03:52 ** GPU Hardware VM is disabled (multispace: disabled, page table updates with DMA: disabled)

Dec 8 19:03:53 Previous shutdown cause: -128

Dec 8 19:03:57 BUG in process suhelperd[172]: over-released legacy external boost assertions (1 total, 1 external, 0 legacy-external)

Dec 8 19:04:51 BUG in process suhelperd[172]: over-released legacy external boost assertions (0 total, 0 external, 0 legacy-external)

Dec 8 20:02:42 ** GPU Hardware VM is disabled (multispace: disabled, page table updates with DMA: disabled)

Dec 8 20:02:42 Previous shutdown cause: -128

Dec 8 20:02:46 BUG in process suhelperd[170]: over-released legacy external boost assertions (1 total, 1 external, 0 legacy-external)

Dec 8 20:03:28 BUG in process suhelperd[170]: over-released legacy external boost assertions (0 total, 0 external, 0 legacy-external)

Dec 9 14:53:21 Previous shutdown cause: -128

Dec 9 14:53:25 BUG in process suhelperd[184]: over-released legacy external boost assertions (1 total, 1 external, 0 legacy-external)

Dec 9 15:19:04 ** GPU Hardware VM is disabled (multispace: disabled, page table updates with DMA: disabled)

Dec 9 15:19:04 Previous shutdown cause: -128

Dec 9 15:19:09 BUG in process suhelperd[182]: over-released legacy external boost assertions (1 total, 1 external, 0 legacy-external)

Dec 9 15:19:38 BUG in process suhelperd[182]: over-released legacy external boost assertions (0 total, 0 external, 0 legacy-external)

Total CPU usage: user 16%, system 10%

CPU usage by process "WindowServer" with UID 0: 2.5%

Extrinsic system jobs:

Extrinsic agents:

com.plexapp.ht.helper

com.spotify.webhelper

com.google.keystone.user.agent

launchd items:

Library/LaunchAgents/com.google.keystone.agent.plist

(com.google.keystone.user.agent)

Library/LaunchAgents/com.plexapp.ht.helper.plist

(com.plexapp.ht.helper)

Library/LaunchAgents/com.spotify.webhelper.plist

(com.spotify.webhelper)

Unsigned shared libraries:

/usr/lib/libcom_err.dylib

/usr/lib/libdes425.dylib

/usr/lib/libgcc_s.10.4.dylib

/usr/lib/libgcc_s.10.5.dylib

/usr/lib/libgssapi_krb5.dylib

/usr/lib/libk5crypto.dylib

/usr/lib/libkrb4.dylib

/usr/lib/libkrb5.dylib

/usr/lib/libkrb524.dylib

/usr/lib/libkrb5support.dylib

/usr/lib/liblber.dylib

/usr/lib/libldap.dylib

/usr/lib/libldap_r.dylib

/usr/lib/libpython.dylib

/usr/lib/libpython2.6.dylib

/usr/lib/libpython2.7.dylib

/usr/lib/libtcl.dylib

/usr/lib/libtcl8.5.dylib

/usr/lib/libtk.dylib

/usr/lib/libtk8.5.dylib

/usr/lib/python2.6/config/libpython2.6.a

/usr/lib/python2.6/config/libpython2.6.dylib

/usr/lib/python2.7/config/libpython2.7.a

/usr/lib/python2.7/config/libpython2.7.dylib

Profiles: 0

User login items:

Macs Fan Control

Google Chrome

Spotify

Plex Media Server

Restricted user files: 39

Font problems: 0

Elapsed time (s): 235

The machine will run (seemingly) indefinitely in Safe Mode. Anyone have any ideas? This feels like it might be a GPU issue to me, but the fact is it does seem to have started since I upgraded to Yosemite.