I don't think, that the guys  will improve anything. Be happy for every workaround you know... and use it and be happy! There are still a lot of bugs in the vetta software, which never will be fixed and even the last Line6Edit update won't fix all functional bugs (for example mic settings for the Flextone).

On the other side the MIDI protocol was created in the 80's just to transfer tiny messages like "which key" was pressed "how fast" and "how long". That's all and this will work with your MIDI interface. But in our case, Line6Edit and the Firmware update transfers a big amount of data, which - maybe - is not matching the standard MIDI protocol. Be happy that it works fine with M-Audio Uno. All guys who are able to afford a Vetta, should have the bucks for this blue box.

The whole MIDI/USB thing is about buffering.

The MIDI protocol is designed to play an instrument in real time with correct timing for the MIDI sequence.  So, it won't deal with buffering where the data flow stops and starts as a memory buffer fills.

Most (nearly all) MIDI/USB interfaces mess up the flow of MIDI data by allowing the USB buffering to start and stop the flow of data.  If there is only a small amount of data involved then the buffering won't come into play.  Like when Monkey just checks what device is connected.

Only a handful of MIDI/USB interfaces will work correctly without interrupting the data flow with buffering.  The M-Audio UNO is one of the least expensive of the proper MIDI/USB interfaces.

Vetta users before you have experienced the same problems and have remedied the problem by getting a reliable MIDI/USB interface.

Of course, the manufacturer of the interface is not going to want to admit any limitation of their hardware, but ask them for a technical breakdown of how MIDI data is buffered compared to a native MIDI interface (one that doesn't route via USB) like what comes out of a MIDI sound module or keyboard.

Anyway, you can either persist with using the interface you have and not transfer data to and from the Vetta or you could get a reliable MIDI/USB interface and be up and running in no time at all.

Another suggestion is to get yourself a sound card for your computer that comes with a MIDI interface.  That way you never have to worry about MIDI/USB.  I have kept my trusty Sound Blaster Live Drive because it has MIDI ports on the front panel, I have never had any problems with MIDI, not ever.

Cheers,

Crusty