I just stumbled onto something called MidiTest. I have not tried it, but something the designer wrote about caught my attention as it >>might<< relate to an issue some people here have had with certain usb-midi interfaces not working properly (possibly with sysex data). If I recall correctly, this issue has come up in connection with e-loader not working with certain usb-midi interfaces.
See the link in the September 25th, 2005 entry here: http://miditest.earthvegaconnection.com/#about
It seems that MidiTest's developer discovered a bug with DirectMidi. Evidently this discovery (and possibly solution) caught the attention of Steinberg.
I am not sure this applies to what some e-mu users have experienced, but I thought it might. The article is on the technical side, but what I am thinking is that it might suggest that the issue is with the drivers for those interfaces. If so, perhaps owners of those usb-midi interfaces can compare version numbers of the drivers to try to see if one range of drivers consistently works while another range consistently doesn't work
From the link:
"This article describes the problems with system exclusive and DirectMusic and offers solutions to the developers of drivers for MIDI hardware and to developers of applications that make use of the DirectMusic technology. The article is targeted at people that are already familiar with either MIDI driver development or programming against the DirectMusic API. It does not offer an indepth description of these technologies."