I've said it before and I'll say it again. There's no way you will get anythning but a guess without some specifics about your project, your render settings and your system. You kind of started telling us about your setup but there are just too many variables for anyone to have a guess at what is causing your problems. We need details. Lots of them.
Feel free to run the Creative Suite Cleaner Tool and reinstall. Doesn't fix your issues, though. As long as your flakey audio device drivers are there, the programs might still attempt to use it. Conversely, all those little failures might relate to the driver crashes or be caused by unsuitable render settings, user privilege and file permission problems and what have you, but we don't know any of that based on your somewhat sparse and vague info...
Somewhat sparse and vague is an understatement - it was late last night when I posted, and I was a bit fried, trying to output a project with 13 versions, and AE crashing (well not exactly crashing - I'll explain later) after every output. First off, my system specs - dual-quad Intel machine with Vista Business SP2 64-bit (all of the Adobe apps have been running seamlessly on it until this problem - no doubt self caused). I'm running the CS6 Master Collection, and everything is on the latest rev, AE included. I have a number of plugins from Red Giant on the system, although none of these were in use in the project. The only plugin in use was Video Copilot Optical Flares, and that's never given me a problem. I have the AE cache set to the Apps drive (oh yes - 500GB OS drive, 500GB Apps drive, and two 750GB Media Drives, plus an 8TB Drobo for backup). As I say, everything has been running just fine for a couple of years. The sound card I talk about below had already been disabled in the Device settings in Control Panel, and I had deleted the suspected drivers, and also disable one which hadn't gone away with the uninstall of the Creative Labs apps. I had set the system back to the on-board sound card (ATI), and I was getting audio fine with both RAM previews as well as renders. The problem was, almost every time I would do a render, using the Render Queue, the fan on my Nvidia GeForce GTX-260 (latest driverss - text file in AE hacked to show it) would ramp up, as it often does on renders, and then the comp would sometimes render, and sometimes the screen would just go black - no crash - system seemed to still be running, but with the fans maxed, and I would have to do a hard boot with the on-off button on the machine. When it came back, sometimes the QT would have rendered, sometimes not.
I was outputting a short station ID to Quicktime, Mjpg-A, at 100 percent quality, audio at 48Khz - nothing custom about it.
I had installed an old (2007, maybe?) Creative Labs SB Audigy LS in an open PCI slot - found some drivers which Creative Labs acknowledged as ok, but were third party. With some changes in Windows, audio was working in AE and everywhere else. Since the problem, I have done a registry restore - I always back up the registry when I add new software or hardware, and I am just about to fire up the machine and try again with the sound card hardware removed, and the registry reset.
OK - I think I nailed the problem - once again the famed PEBCAC acryonym comes into play (Problem Exists Between Chair and Computer). When I installed the Audigy sound card into the PCI slot, which lives under the PCIe slot where my Graphics Cards lives, I tucked a small bundle of SATA cables out of the way. I tucked them right into the hole in the Graphics Card where the cooling fan sits - of course, it being on the bottom of the card, and mounted low on the mobo, I couldn't see it.
I decided to do one last dummy check before booting up the computer with the registry restore (older registry) on it, and, while double checking the graphics card to make sure it was seated, felt the cable bundle, moved it out of the way, and realized that the fan opening was right where the cables had been tucked. On rebooting, I am noticing much less fan noise on outputs from AE, and nothing has crashed thus far, so I'm hoping it was just my stupidity...and that the graphics card was overheating and locking up, causing the black screen of embaressment...thanks again for your help...