Freeze (*possible* hang in MAIN graphics engine) after watching long flash video

Make a "Genius" appointment at an Apple Store, or go to another authorized service provider. You may have to leave the machine there for several days.

Back up all data on the internal drive(s) before you hand over your computer to anyone. There are ways to back up a computer that isn't fully functional—ask if you need guidance.

If privacy is a concern, erase the data partition(s) with the option to write zeros* (do this only if you have at least two complete, independent backups, and you know how to restore to an empty drive from any of them.) Don’t erase the recovery partition, if present.

Keeping your confidential data secure during hardware repair

Apple also recommends that you deauthorize a device in the iTunes Store before having it serviced.

*An SSD doesn't need to be zeroed.

No one in this huge community can fix a faulty logic board, which is what you have.

Really don't believe this is a hardware problem… too many reports of it. and the nature of it is that it occurs so infrequently but each time requires a reboot to resolve. Have tried quitting all processes and applications to narrow down but continues to happen; always after a period of sleep and never while working. This issue appeared at some point following software changes, so am hopeful of an OS update resolving it.

I have this exact issue. Same messages:

13/10/14 18:35:02,000 kernel[0]: Head and tail pointers match!  Engine is idle.
13/10/14 18:35:02,000 kernel[0]: This can happen for a variety of reasons, but the most common reason is that we have been
13/10/14 18:35:02,000 kernel[0]: asked to wait for a stamp which has never been submitted to the hardware!
13/10/14 18:35:02,000 kernel[0]: MAIN ring is NOT waiting on an event
13/10/14 18:35:02,000 kernel[0]: MAIN ring is NOT waiting for a semaphore
13/10/14 18:35:02,000 kernel[0]: MAIN ring is NOT waiting on an event
13/10/14 18:35:08,000 kernel[0]: ****  Debug info for *possible* hang in MAIN graphics engine  ****
13/10/14 18:35:08,000 kernel[0]: Head register = 0x00000000
13/10/14 18:35:08,000 kernel[0]: head offset  = 0x00000000, wrap count = 0
13/10/14 18:35:08,000 kernel[0]: tail offset  = 0x00000000
13/10/14 18:35:08,000 kernel[0]: ring control  = 0x0000f001  auto report enabled, not waiting for event, semaphore not waiting, length = 0x010 4KB pages
13/10/14 18:35:08,000 kernel[0]: timestamp = 0x26c72d3
13/10/14 18:35:08,000 kernel[0]: Semaphore register values:
13/10/14 18:35:08,000 kernel[0]: VRSYNC: (0x12044) = 0x26c72d3
13/10/14 18:35:08,000 kernel[0]: BRSYNC: (0x22040) = 0x26c72d3
13/10/14 18:35:08,000 kernel[0]: RVSYNC: (0x 2040) = 0x0
13/10/14 18:35:08,000 kernel[0]: BVSYNC: (0x22044) = 0x56e8e
13/10/14 18:35:08,000 kernel[0]: RBSYNC: (0x 2044) = 0x0

I also feel like it's mainly during the watching of videos. I already had poor performance with Firefox and Flash videos since long. With Apple I never can differentiate between hardware and software issues, so it can be a broken logic board/GPU or simple driver issues.

Has this been resolved since your post?

No. Unfortunately still not resolved although it has only happened once in the last few weeks for me. Maybe Yosemite will fix it... or maybe it won't

I, also, have been experiencing this problem recently (past few months?). Just got around to checking the logs today and Google brought me here, when I searched for:

'kernel[0]: stampWait: Overflowed checking for stamp 0x0 on MAIN ring: called from'

As Pagedan states, definitely occurs during period of inactivity. I've never seen it happen while I was actually using the machine. Seems related to stopping videos and coming back to them much later.

Model Identifier: MacBookPro8,2

BTW, I had my Book checked at the Apple Store 3 months ago when they replaced the battery.

Also, it doesn't totally hang. It wakes up every couple minutes for a brief period and then hangs again. I was able to do a Restart, which took a long time.