The differences between the two logs indicate that the version of VC is not the only variable that you're changing. That will make it more difficult to isolate the problem using just these logs with no information about your setup in general.
Can you please clarify:
1. Are you running both of these instances of VC on the same computer, or is one on one computer, and the other on a different machine?
2. Is XBMC installed on the same machine as VC in both cases?
3. Your command configuration appears to be different in the two log files. For example, in the 2.125 log, your "launch XBMC" command is doing all kinds of weird extra things like streaming a playlist (not in XBMC(?!?) but in VLC, it looks like) and then minimizing windows and changing system volume and focusing new windows, and a bunch of other things, and then there are some empty actions etc. In the other log, the "launch XBMC" looks more standard, and works properly.
4. In your 2.125 installation, are you generally having problems with XBMC commands, or just the new play music video command? (If so, perhaps you should review the VC installation tutorial for setting up VC with XBMC to make sure you have all the settings correct in both programs.)
5. In that 2.125 installation, has it properly generated your payload XML file for the music videos yet? There would be no way for that command to work until such time as the payload XML is properly generated. In other words, there would be no point in even trying the command as long as the payload XML file is empty.