Hi pmdaniels,
Since I'm in Euro time right now, I'll try to cover some basic ground before James gets up. First, it's a bit hard to help you without understanding your setup or more about when VC is not recognizing you, so it would be helpful to provide more information in the future. The following is offered without knowing anything about your system setup.
If VC is in green listen mode and is claiming "VC.NotRecognized" *every* time you issue a command, rather than just some of the time, that may signal one kind of problem. If it understands some things but not others, that might signal something else.
If you have multiple microphones set up, it might be listening to the wrong mic. Alternatively, you could be saying a command that's not actually in its list of commands. Or an existing command you're trying to use may have a parameter that isn't properly configured for your particular computer set-up (for example if it's looking for files in one directory but you keep them somewhere else, or if you're asking it for something from your media library but haven't yet run GenXML), etc.
You could start by taking a look at the FAQ in the wiki--in particular,
http://voxcommando.com/mediawiki/index.php?title=FAQ#Why_doesn.27t_VC_understand_me_all_the_time.3FIf you think your mic is set up properly for VC, try first to issue a very basic command, for example: Manually put VC in "Listen mode" (green) and then tell it "Don't Listen" or "Ignore Me" or "Buzz off". It should then switch to standby mode. Or, vice versa: Put VC in yellow standby mode, and tell it to "Pay Attention". It should switch to the green mode.
If that works, then VC understands you. So then you can move on to figuring out what's wrong with the commands it isn't recognizing. If it's specifically having difficulty understanding your XBMC-related commands, this would be helpful to know.