Ultra 2+ [Hardware Error]: Machine check events logged

Came home from a trip yesterday and realised my U2P was turned off. Turned it on and looked at the logs

System log has this from 9 Nov prior to whatever happened to turn it off.

Nov  9 19:32:44 surire noflushd[1787]: Spinning down disks.
Nov  9 20:08:07 surire noflushd[1787]: Disks spinning up after 35 minutes.
Nov  9 20:08:12 surire kernel: CPU2: Core temperature above threshold, cpu clock throttled (total events = 1)
Nov  9 20:08:12 surire kernel: CPU0: Core temperature above threshold, cpu clock throttled (total events = 1)
Nov  9 20:08:12 surire kernel: CPU0: Core temperature/speed normal
Nov  9 20:08:12 surire kernel: CPU2: Core temperature/speed normal
Nov  9 20:10:36 surire kernel: [Hardware Error]: Machine check events logged
Nov  9 21:33:49 surire noflushd[1787]: Spinning down disks.
Nov  9 21:33:58 surire noflushd[1787]: Disks spinning up after 0 minutes.
Nov  9 22:26:40 surire udhcpc[2270]: Sending renew...
Nov  9 22:26:40 surire udhcpc[2270]: Lease of 192.168.24.65 obtained, lease time 86400

It has UPS and there was no power fail, but on restart it went through all the power up phase and in the log shows

Nov 10 21:09:37 surire kernel: EXT3-fs (md0): recovery required on readonly filesystem
Nov 10 21:09:37 surire kernel: EXT3-fs (md0): write access will be enabled during recovery
Nov 10 21:09:37 surire kernel: EXT3-fs: barriers not enabled
Nov 10 21:09:37 surire kernel: kjournald starting.  Commit interval 5 seconds
Nov 10 21:09:37 surire kernel: EXT3-fs (md0): orphan cleanup on readonly fs
Nov 10 21:09:37 surire kernel: ext3_orphan_cleanup: deleting unreferenced inode 12517
Nov 10 21:09:37 surire kernel: ext3_orphan_cleanup: deleting unreferenced inode 12938
Nov 10 21:09:37 surire kernel: ext3_orphan_cleanup: deleting unreferenced inode 3138
Nov 10 21:09:37 surire kernel: ext3_orphan_cleanup: deleting unreferenced inode 3136
Nov 10 21:09:37 surire kernel: ext3_orphan_cleanup: deleting unreferenced inode 3123
Nov 10 21:09:37 surire kernel: ext3_orphan_cleanup: deleting unreferenced inode 3117
Nov 10 21:09:37 surire kernel: ext3_orphan_cleanup: deleting unreferenced inode 2924
Nov 10 21:09:37 surire kernel: EXT3-fs (md0): 7 orphan inodes deleted
Nov 10 21:09:37 surire kernel: EXT3-fs (md0): recovery complete
Nov 10 21:09:37 surire kernel: EXT3-fs (md0): mounted filesystem with ordered data mode

So, clearly it looks like it was hot at some point. It has been hot here, but the room where the NAS is is never above 25 degrees and it was completely idle as no one was using it.

Currently the room is 22.1C and the Status->Health shows

Temp 1	66 C / 150 F [Normal 0-80 C / 32-176 F]		OK
Temp 2	29 C / 84 F [Normal 0-65 C / 32-149 F]		 OK

Any ideas?