I am currently experiencing MIDI only playback dropouts (not audio) when running through a new MOTU MIDI Express XT interface. I am using Sonar X3 Producer, WIN 8.1, plenty of memory and processing. When I run the same MIDI sequence through the old Cakewalk Music Connector 1 interface there is no problem no matter what combination of audio and MIDI I use. When I run the MIDI sequence thru the MOTU interface with the audio tracks muted there is no problem. When I turn on Audio tracks, the audio plays flawlessly but the MIDI track experiences dropouts seemingly randomly. Dropouts are only  few beats and when the MIDI returns it is right where it is supposed to be.
 
Lots of stuff online about how this interface doesn't play well with Windows. Some folks say it works perfectly and others say it does not. Right now I'm one of the does nots. Lots of info out there on audio dropouts but none on this type of problem. Anyone have suggestions on solutions?

Make sure it's on a USB2 port instead of USB3.
 
If already on USB2, try a different (USB2) port.

Also I found this older post -- specifically, the 3rd paragraph, that mentions a timing problem and fix for that device:
 
http://forum.cakewalk.com/FindPost/3066767
 
It's worth trying...

Another generic fix for MIDI dropouts is to set your MIDI prepare buffer to 500ms or higher. (in Edit > Preferences > MIDI - Playback and Recording)

Update...I'm finally back up and running. After rechecking all the clocks (which were already correct) and going through looking for any relevant event and error messages, I tried one last ditch shot in the dark to see if my USB throughput was being limited somehow internally to the PC. I combined the 3 USB connections (2-2.0 and one 3.0) into one externally powered 3.0 hub and ran it through the 3.0 on my workstation. Been up and running all day without a glitch.
 
The MOTU MIDI express XT is operating as advertised with Windows.

If you have got a spare PCI slot in your computer I found the ideal way to go is to get a PCI card that has 2 or 4 USB ports on it. Run your Midi interface on that and nowhere else. I get the best performance by far that way. This works because this USB port is totally independent of every other USB port on your machine. Be careful trying to run a big audio interface and midi interface on the same USB port as well. Not a good idea either. 
 
Also in the original post referred to here back in 2014 it was mentioned that in some DAW's the midi timing is tied to the audio clock.  In Sonar it is this way I am pretty sure.  This is not the case in Studio One by the way and it is one of the reasons I left Sonar.  In Studio One external midi timing is super fast and spot and totally independent, no matter what the audio side of the program is doing.  As it should be. 
 
I am keen to know what the Midi Express is like because currently I am using a Steinberg Midex 8 interface (on Win 7) but once I upgrade again this won't work any longer and the MOTU is the only thing left I think that runs on the latest Mac and Windows OS systems.  So I am hoping it is OK!

Jeff Evans
If you have got a spare PCI slot in your computer I found the ideal way to go is to get a PCI card that has 2 or 4 USB ports on it. Run your Midi interface on that and nowhere else. I get the best performance by far that way....

+1
 
I've been using this strategy with audio interfaces for years.  Has worked equally well with USB and Firewire (The latter with TI chipset). 
 
With newer motherboards best to go with PCIe.  Even though they may still have PCI slots, these are often bridged (sharing resources) which defeats the whole purpose of a dedicated bus.

I took delivery of a MOTU Micro Lite yesterday.
 
The manual for that device is also the manual for all of the MOTU MIDI devices. It makes no mention at all about having to use USB 2 or USB 3. It just says "USB."
 
My laptop only has one USB 2 port and three USB 3 ports. I always reserve my single USB 2 port for my OCTA-CAPTURE/QUAD-CAPTURE, because everyone says that's what you should do.
 
I'm going to have to use a USB hub now, because my three USB 3 ports are taken up by mouse, keyboard and MIDI keyboard. So it's likely I will stick the MIDI keyboard and Micro Lite in the hub.
 
Fingers crossed, all will be okay... Don't fancy buying a desktop any time soon...