Welcome to the EVGA forums
Please post your system specs, OS version, currently installed Nvidia driver version and monitor details for review..
 
The Asus AISuite is -known- to have terrible issues with Nvidia drivers for which is was not designed for... (thats ALL current Nvidia drivers)
It should NOT be installed or used at all because of this.
 
Other programs like HWMonitor, AIDA, SpeedFan Etc.. also use injectors into the Nvidia drivers to monitor videocard sensors and for control...
These can all have the same issues as the AI Suite, with newer drivers and videocard sensors
 
The first failure sounds alot like a SMB conflict (a program(s) using the sensors) and then you damaged your Nvidia driver install by using Device Manager
*(as per Nvidia, Device manager should NOT be used as a Microsoft patch has changed the behavior and Nvidia driver installs can now be damaged by using it)
 
The second could simply be a bug from a new game...
 
Its unclear "how" you installed your Nvidia driver after all of this (posted above) and then you put in Precision.
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You need to PROPERLY recover from the above before starting testing
 
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Shut down and uninstall EVGA Precision
*VERY IMPORTANT: during the Precision uninstall a box will pop up asking to save data. You MUST answer -NO-
After the uninstall is complete, REBOOT once (do NOT skip this reboot)
 
Now manually download Nvidia 337.50 BETA (or the driver of your choice)
--DO NOT USE the GeForce Experience to download or install--
*If you have the GeForce Experience installed, go to Control Panel/Programs and features and UNINSTALL it
 
After downloading your driver of choice...
Launch the installer, choose -only- CUSTOM Mode
UNCHECK -ALL- Nvidia driver components, except for Graphics driver and PhysX (nothing else checked)
*Do make sure the you put a check in the box for "Perform a clean install"
Now install the driver
After the install is complete, reboot your computer once (do NOT skip this reboot)
 
You may now install Precision X
Use ONLY version 4.2.1
*It is suggested to -uncheck- the RivaTuner (RTSS) addon during the install
Set Precision to start at boot, and use a aggressive user fan profile for testing (example below)

 
*remember that Precision must be running for the fan profile to be active.
 
All of this should get your Nvidia driver in CLEAN and give you a STRONG fan profile for further testing
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This is not to say that something else might be going on...
But getting your drivers back in -correctly- and having a strong fan profile will rule out drivers and temps and allow for further testing 
 

@maniacvvv - I'll give your instructions a shot. Is it necessary to Uninstaller the nVidia drivers first before manually downloading the latest drivers from the website? Should I select "clean install" once I'm in the driver installer?

You're spot-on Randolla. A clean install should be sufficient.

Please post your complete system specs, OS version, currently installed Nvidia driver version and monitor details for review..

A single GTX 680 would be underpowered for 2560x1440 for many games...
What GTX 680 model number do you have? how much Vram?
 
We also need to know what CPU you have, what speed its running at and how much system ram you have.
 
Right now with the info you have posted..
-->stuttering and crashing in certain games would be -normal- at 2560x1440 with higher settings, as that takes more Vram and horsepower than you appear to have available.
 
You should download the free Unigine Heaven 4.0 Benchmark  https://unigine.com/products/heaven/download/
And test for system performance with your hardware as its configured.
 
 
 

Yeah, for some reason this forum doesn't like links. They work fine in the post preview, but disappear after I hit Submit Post.
 
Specs: 
Windows 7 Home Premium 64-bit SP1
CPU: Intel i7 3930k @3.2GHZ
RAM: 16GB DDR3 @ 667MHz (9-9-9-24)
MOBO: Asus P9X79 PRO (LGA 2011)
GPU: EVGA GeForce GTX 680 (2GB Superclocked version)
 
 

While it's not going to be the greatest performance, the 680 should be sufficient to keep you over 30FPS in most games at nearly maxed settings. I ran a single 760@ 2560x1440 for about a month, it managed to average 30-50FPS in most games, and 60-90 in SLI. With at least Team Fortress 2 running properly though, it doesn't sound like a hardware problem. If it were, it would manifest in every game. 
 
I suspect it's a driver issue somewhere, maybe with the Nvidia HD audio controller driver. I've seen that cause stuttering and low performance before. Try going through our FAQ and see if it makes any difference: http://www.evga.com/support/faq/afmmain.aspx?faqid=59211. Also make sure you've got the Power Management setting in the Nvidia Control Panel set to "Prefer Maximum Performance". That should help with the dramatic swing in frame rates.

If you follow the FAQ, it tells you how to disable it semi-permanently so it won't come back on restart. Basically you'll disable the Nvidia High Definition Audio Controller that's on the same PCI Bus as your video card in the Windows Device Manager under System Devices. Just uninstalling the driver doesn't do it, and it gets reinstalled as you've noticed. Disabling it under System Devices basically shuts if off at the motherboard level, and when you do a clean driver install you'll notice the HD audio driver isn't even available anymore.

did you fix your problem?