In the Link-outs section of the VSX Detail Sheet, there is a drop-down to menu for selecting and accessing various external Web resources relevant to the detailed object. Everything seems to be linking-out ok except for VSP. It looks like a malformed GET is being passed.
e.g. for MIRA one gets: http://www.aavso.org/vsp/?pickname=omi%20Cet
Of course I notice this only now because I'm a big fan of it :-)