Robomusic
Here is the Deal. ASIO4All is not a true ASIO driver, it is a wrapper that makes the windows WDM driver think it is ASIO.
Interfaces like the Lexicon come with driver install disks that contain true native ASIO drivers. You should find the driver here http://lexiconpro.com/downloads.php
The reason Cubase sees a driver might because Cubase is a Stienberg product, and yes you guessed it they created ASIO drivers.
The big question is did you install the Lexicon driver disk, or just the cubase install disk?
If you want MC5 to work on ASIO drivers, you need to make sure they are installed properly.
Not only did I install the Lexicon driver, I used the most current driver via the web - not the disk it came with. There is no specific "ASIO" driver for the Lexicon that I can find. I installed it from alphadriverinstaller.exe and it's a very basic installation with no options. I've google searched Lexicon ASIO driver, searched the Lexicon site to no avail. I'm guessing it should be part of the basic driver installation, but it's not.
In the audio set up, on the second tab where MME32 is selected by default, I choose ASIO. After closing and re-opening, MC tells me there's no playback device, and gives me no options to choose from. I change it back from ASIO to MME32 and I get Lexicon IN/Out as the only option for the playback device, but no option for Lexicon ASIO.
Oh, and I use MC4, not 5. Not sure if that makes a difference. Does 4 not support ASIO?