I am having a similar problem with dropouts and latency issues.  I have a quad core Windows 7 64bit machine  with 16gb of ram, a Presonus Firestudio Project interface that I run at 44.1 and 128ms.  I do use a lot VI's including heavy hitters like Omnisphere, Trilian, Ivory II, VSL, SSD4, but my system has enough power to handle those.  Even if I set the latency to 1024 ms I still get dropouts, though not near as bad.  I also use Pro Tools 11 and do not have any issues.  My issues go away when I uncheck use multiprocessing engine in preferences, but I of course run out of resources for large projects and that is a bandaid, not a solution.  I am curious if your latency and dropout issues disappear if you try this.

Here is the solution to your problem - http://www.audio-mastering-mixing.com/faq---q-a.html#32
 
Cj
 

I'd hesitate a guess,and say Tascam.
 
I had one of those US600's and only got sound for 10 minutes in 3 weeks before I got something different.
 
I now have a Cakewalk VS100[not real low latency,but reliability is where it's at for me],and it's been the most reliable unit,after going through hundreds of dollars in USB interfaces.
 
Sorry I'm not really helping,but if you got that Tascam to actually work before,you must know something!
 
Jim Roseberry's help is from someone who knows all the variables.
Bob

@ry1633 - several folks have done some homework on your behalf, myself included, and we have asked you multiple times to try using ASIO as the driver mode.
 
Please post back with the results of your switching the Driver Mode from WDM to ASIO.
 
Bob Bone
 

well...I changed to ASIO drivers - and so far playback is *much* cleaner with no drops or anything.  I haven't had a chance to do any new tracking yet.   will post again in a day or two when I get a chance to get some more work done.
 
-Ryan