Alright I checked the version of xlabel my theme is using and looked in the readme and it says the syntax is [meminuse]. So then I looked to see what version the working theme was using and it was 4.1.5 so I changed the theme.rc of the version I'm using to 4.1.5 and it doesn't display any of it now, the top panel of my theme now reads exactly this:
"CPU [CPU] :: RAM [memInUse] :: C: Free [diskAvailable('c:', %)]% :: Uptime [uptime] :: IP Address [ip] :: Time [time('h:nn:ss')]"

Does 4.1.5 have some kind of dependency I need to load as well?