What version number of VC are you using, and what version of XBMC?
Any chance you've changed the default port in the xJson plugin settings from 9090 to something else (by accident or on purpose)?
Something similar occurred a few months ago, and it turned out the user was not using the default port in XBMC:
http://voxcommando.com/forum/index.php?topic=1513.msg13144#msg13144----
Otherwise:
When you say XBMC actions aren't showing up in the history panel, do you mean that XBMC
events are not appearing, or more than that?
If it is just the events, are you seeing other, non-XBMC events?
Is this true even if you reboot your machine?
If the problem persists after a reboot, please enable logging in VC, issue some of your XBMC commands, and then post the complete log as an attachment.
thanks