ISSUE: Out of nowhere, when I stated AC3 from the Desktop shortcut (game has been working fine at my triple monitor setting of 5760x1080), it would either treat the middle screen like it was a surround and start up in only the middle third of it, or after the title screen, it would threat the middle screen as if it was the entire three-screen surround setup and load the entire FOV of 5760 on one screen, looking "smushed." Shortly thereafter the game would crash and I would (not every time) get the "ASC3P.EXE has stopped working" message. I uninstalled the game, keeping save game files. I restarted my system, re-installed the game off the DVD, ran the patch updater, then restarted the system again. Alas, to no avail, same error/message.
EDIT: (PARTIAL) FIX: I right-clicked on the Start Menu game file (in my case Start Menu/All Programs/Games/Assassin's Creed III), and clicked "Run as administrator". It worked. I deleted the current Desktop shortcut, and sent a fresh one back to the Desktop by right-clicking on the same file and Send To/Desktop(create shortcut). That worked too. Hope this helps someone else out.
NOTE: I just reinstalled a fresh copy of Windows 7 Home Premium (Retail) on my dedicated boot SSD and all drivers/settings/utilities are up to date. I've included system specs for reference.
i7 2600k @ 4.5Ghz 1.30V on Noctua NH-D14 24/7
GIGABYTE G1.Sniper 3
G.SKILL Ripjaws X Series 8Gb (4x2Gb) DDR3 @1600Mhz
2xGTX 680 4Gb Classified SLI OC (+80/+500) 1267Mhz/7012Mhz 310.70 Beta
3xSamsung B2430H DVI
OCZ Agility 3 64Gb SSD SATA III/6Gb
1TB Western Digital 7200 RPM SATA III/6Gb
COOLER MASTER Silent Pro Gold Series 1200W
COOLER MASTER HAF 932 Advanced Blue Edition