I've had an odd night with my Mac Pro, and I'm now stuck with a problem.
I was having spotty wifi connectivity issues with my early 2008 Mac Pro (2 x 2.8 quad core Xeon, 14GB RAM, Mountain Lion with all software up to date). I opened the case and found that one of the two antenna wires (wires #1 and #3) were loose, so I reconnected the wire, vacuumed the interior, and closed everything up.
I reattached all cables and tried to restart. The system wouldn't start up. I would get the whirrr sound of a normal startup, but it would run for 1-3 seconds and shut off. I disconnected the power cord. I reconnected it. I connected it to another outlet. I tried a different power cord. No luck.
I took drives 3 and 4 out to see if that gave me visibility to anything I might be missing, but they didn't. Oddly enough, the system started once while they were out. I shut down and carefully reinserted each drive. No start up again.
Long story short, I tried ever combination of hardware inserted and removed, periferals connected and disconnected, and options for power that I could think of. I got no where and was starting to assume power supply. I ran across a thread on the topic where a responder suggested to the OP to hold the power button in for a long time. I did (60 seconds) and presto, after releasing I had power and was able to boot normally except that my fans were now running at full power, and were quite loud. I put the system to sleep and woke it. No luck. Powered off, and prayed it would restart... it did, but with full force fans again. I read an article about SMC reset and tried that. After completing that procedure my system would not start again. I held my breath and tried another 60 second press of the power button and I am now rebooted, running my machine, and posting this question. The fans are running so strong that my feet are cold.
Any ideas / suggestions? I now have wifi, a clean machine, I'm using no system resources (activity monitor says user is about 1%, system is 0.6%, percent idle is 98-99%). Fans are loud enough to be heard upstairs above the office where the mac is located.
Any help would be greatly appreciated.