@Nick, are you on KDE? I've had this for a while, and I suspect it's related to https://bugs.launchpad.net/ubuntu/+source/gnucash/+bug/1319523 which links to https://bugs.gnucash.org/show_bug.cgi?id=730195. It could be some issue between GNUCash's quickfill libraries (yes, they wrote their own) and KDE's implementation of whatever GTK libraries upon which it depends.
I don't get the problem on my Windows installation.
