JP it seems, based on this thread on the vBulletin site, to be an issue unique to a recent version of >>
Chrome <<
Notice in post #38 one of the developers suggests that pressing the Enter key first should restore the space bar function for Chrome users. There are others in that discussion who seem to be trying to determine some fixes - I'll keep an eye on it. The version of VB I use (4.x.x) is not under current development as it is not the latest version so it's doubtful any "official" fix will be implemented any time soon.