Hi everyone.
I just read almost all the "UR 44 drops outs " post in this forum, but i didi not find a single person that have mi exact same issue with this hardware.
I will try to make it short.
I just update my hardware. I had a Dell Vostro 3500 with the cubase 7.5 version installed and the UR 44 works just fine.
I just need some more power to put more vst in real time composing and mixing, and the vostro was lefting behind.
I did not have much of a budget so i bought a second handed desktop pc:
MOBO : ASUS P8H61-M PRO
CPU: i7 2600 (second generation)
RAM: 8 gb 1333 mhz
HDD: SAMSUNG 1 tb (don´t recall the model)
OS: Windows 8.1 AND Windows 7 both 64 bit
All my test are in both operating systems.
Ok the problem is this:
The minute windows is trying to playback any sound the left channel reproduce an insane amount of noise and distortion.
But only in the DAW channel of the UR44 virtual mixer.
If i connect a microphone an monitor thru the UR44 there is no distortion.
In windows 8.1 this noise will last forever.
In win 7 it will continue until I close the application that I was using
I have tried everything (almost)
Different usb ports
A ssd card reader which is connected to the mobo.
Differents usb cables (long and short)
Diferent AC sockets
Different HDD
Disconnecting the nvidia graphic card
Disconnecting all other HDD
Different power supply (thermaltake model and Vitsuba model)
I tweak several Bios configurations with no change (hyper threading, power mode, usb battery charger option etc.)
I just run out of ideas.
So if anyone has this problem or if someone has a single clue of what´s happening, please help me 
The 2 things that i might try is to buy a AC power stabilizer and an active usb HUB (not much hope in that becose the card reader in the mobo is connected to AC)
Many thanks in advance