Any other suggestions would be greatly appreciated!

It seems to that you have a USB problem. Is your computer USB 2.0 or 3.0? 

Did you reset the Fatar? Mine occasionally needs to be reset. 

Thanks daveny. My computer has it all both USB2 and 3. I use USB2 for VS-100. I am not sure what you mean with resetting Fatar? I have a main AC-switch to all devices (computer, pc-screen, preamps, speakers and the Fatar SL-880). I turn on the main switch, turn on on computer go in to Sonar and...no midi in now 2/3 start ups.

I also have a Fatar SL-880. To reset it, press and hold down the Up, Down and Enter/Edit buttons while powering it up and then release them. It will wipe out any setting you had, but it resets the keyboard back to factory settings. 

I asked about the USB 3 because I have read in the forum about people having problems with USB 3. If the reset doesn't work, then search the forum on USB3. 

Thanks Dave! I'll try that.

Did a reset of my Fatar Midi-keyboard but the problem persisted. In BIOS I disabled USB3, on-board soundcard and BlueTooth Controller. This resulted in loss of wireless USB-network adapter (I swear it's USB2!). The Blue Tooth Controller was reinstalled during start up I guess due to plug'n play, which is funny because I disabled it in BIOS... Switched to another USB-port for the WiFi-connector and the internet came back. Opened Sonar and there they were, both MIDI-inputs and outputs as well as MOIDI-controller, powered down, did a couple of restarts and YES still there, solid as a rock. Keep my fingers crossed. Thanks everyone for advices!

Hmm. ASUS have an interesting BIOS-update with among other things improved USB-stabilty. Sounds just exactly what I need eh. I'll flash BIOS and set all values to default and report back if you're interested.

Glad you're making progress. Yes, please report back. Others may benefit from your experience. Seems like USB 3.0 still has some problems.

Still works flawless after updated BIOS. :-)