Hi, did return or fixed it? 
Im at editing an .XML for that Keyboard, usual final step before applying the “Fist of Fury” and see if the if the KEYLAB 49 can at least fly if not able to do what Arturia claim for the Transport. I would not let something like that drag my name if it would be Glen… but guess what? I’m not Glen.
I do have an AKAI MPK 225 and it work just fine in CUBASE 7.5 (nice tool) Same thing with the new M-audio Axiom air 61 (but for this one, I had to install the Win 7 Pro Drivers (64bit) instead of those offer for Win 8 Pro 64bit to make more stable. Work for me. M-audio is now avid and their deal is with ableton, not CUBASE like Yamaha does.
What work too is a 24" touch screen from SONY that I can control anything on the screen on the fly. l also use a Bamboo tab to replace the mouse (yes, the one invented by Xerox a million years ago) anyway.
I made it work but I can’t remember what I did… sorry. But at least there is hope.
1- Yes everything need to be updated: firmware, software, and my glass of wine…
2- I add the KEYLAB49 to CB7.5 via “Device setup…”
3- added a generic device, from which I selected the new controler.
4- I know at least I did check what CC I could be apply by clicking the Learn , then confirm on the lower section that in fact it was a Controller / Device / Transport / and the “test” [pad] 13 would gladly work, but not for [PLAY]. But it would recognize LOOP as Cycle selection.
5- then in “Transport” menu at the bottom there is a Project Synchronize Setup… in there I set :MC Master Active: then MMC Slave active: on top I use VST System link… and selected the KEY 49 midi IN every time (no out if all USB)
I Downloaded the MIDI control center from Arturia, (same tool to update the firmware) and I check what number was associated with different controler. 11 was for a “volume” one in Cubase and for the foot pedal plug in the KEYLAB 49.
went back to device manager, select one of the unassigned control from the list, (the one above the Transport series) and made one for the sustain pedal. Back in MIDI Control center and by selecting something else than expression pedal 11: Sustain 64, reversed the range full 127 to zero 1 I send the update to the keyboard. (pedal is a Roland set to variable ) plugged in Expression pedal in the KEYLAB. a must.
note: MIDI Control Center will NOT update the keyboard if cubase is running.
I spent endless time fixing something that we should NOT have to fight with… Yes that one is for you “Glen, I would like to have feedback”.
Best of Luck to you all.
Please if you found out exactly what made it work, please let me know. but I’m sure there is something there that fixed it…
More note: The [PLAY/Pause] button on The KEYLAB 49 need to be press with conviction… for some reason it need to be held a bit to work
not the case with the other ones. (not the case in Arturia’s application)
That was my bitching part… I need to say that the builth of the KEYLAB 49 is just awesome. Way better than the Axiom 61 @ $500 clearly made for ableton. The level of tweaking of all the knob and slider is a 9/10. Sorry M-audio but Arturia provide a miles ahead quality for the price. and thanks for the 5000+ sound that came with it, and can be use in CUBASE 7.5 
I will keep my MPK 225 for all my BASSE audio instrument, the PADS are really nice and can be colour changed . (yes, we say Colour).
First post in good faith, if I Bitch a bit I also found part of a solution not really easy to find.
Ciao,
F.