Tascam US600 problems

Does anyone here use a Tascam US600 interface?  I seem to have started having a lot of problems with mine recently.  I've used mine for more than 2 years now with X1, X2, and X3, and most of the time it's been rock solid.
 
But in the last two weeks, since I've added the CA-2A plugin, I've had a lot of dropouts and crackles with the US600.   I've played with all the latency settings and updated the drivers, rebooted about a million times, and still had difficulties.    The US600 used to work great, but has been very flaky lately.
 
Since I am in the middle of a project, I don't know if I want to make a major hardware change but I'm starting to get very frustrated.
 
Anyone have any tips, tweaks or advice on the Tascam US600?  If it's going to be this unstable, I think I'm going to ditch it and get something else   I've started to look at the Focusrite 18i8 and the Presonus 44VSL.   I'd like a 4-input USB 2/3 box.

My US600 used to be pretty stable.   Just recently I bought the CA-2A computer which I really love.   But now my Tascam has been really acting up - where it used to be fine.   Lots of crackling, then I have to reboot my machine, start Sonar in Safe Mode, and do all kinds of stuff.   Frustrating - especially when I've done everything I'm supposed to - latest drivers, latency settings, etc..    ugh :(
 

Yeah I may EBAY mine this weekend or early next week if I can't get this ironed out.  Probably will get the Focusrite I8i8, or Presonus Audiobox 44VSL.   And the new Tascam 4X4 actually gets really good reviews so I might have to take a look at that one too.