A couple of weeks ago my Mac Pro (Early 2008) started failing to wake properly from sleep – basically it would boot from scratch rather than awaken.
PRAM zapped and all the usual stuff you see written across various forum. Then at the point of installing a replacement backup battery, I noticed a bright red light on one of the RAM risers.
Cutting a long story short, one of the RAM modules has failed. Checking the system profile, 4Gb of installed RAM is missing. The mac has wisely ignored the failing bank of RAM, but it would have been nicer if it had also alerted me to the fact prior to looking inside.
End result: physically removed the modules on the failing bank and now sleep/wakeup works as normal again. Fingers crossed the memory supplier will replace the failing package on their lifetime warranty.
(Update: August 2018, I should have updated this at the time, but Crucial sent a replacement module very quickly and that has worked without fault ever since – the machine is still in regular use at time of writing)
I’ve been having this same issue with my Dual-Core 2.66 Mac Pro (1,1) and this post helped me get to the bottom of it. I pulled a failing OWC 2GB RAM module out (no indication it had failed until I opened up the tower and saw the red light) and now the machine wakes from sleep with no problem. Thanks.
Mac Pro early 2008 2.8GHz Intel Quad-core Xeon with sleep-wake issues.
I also had this problem, a few mornings ago the Mac crashed and restarted rather than waking from sleep.
The following night I heard it do the same 3-4 times so I shut down and the following day I searched the web for the problem.
There was plethora of Sleep-wake crashes associated with Retina MacBook Pros but nothing on the MacPro until I found this post.
Not only the same problem but the same machine, and when I looked inside the same red light. Checking the RAM in About this Mac I discovered I had 10GB, all on the same A Riser, nothing on the B Riser, odd since it came with 4GB (2x 1GB & 2x 1GB) and I had installed an extra 8BG (2x 4GB on the A Riser) so there should have been 12GB. One of the original 1GB chips had failed and of course the system ignored its partner.
Simple job, order another 2x 4GB RAM for next day delivery, fitted it and Bob’s your proverbial.
Did a short Sleep-Wake and that worked, hoping to be able to put the MacPro to sleep as per normal this evening.
I hope this helps others with the confusing issue because it is (seemingly) easily resolved.