I have the same problem (pidgin 2.10.3 on mint 13 with unity and backport). I can also make pidgin show up when I remove .purple/prefs.xml.
But then, the window frame (title bar with minimize, maximize and close icons, drag corners) behaves as if it weren't there.
E.g. I can't drag the pidgin window because when I click the frame, the click goes through to the window below it, or to the desktop if there is no such window.
But I can use the contents of the pidgin window as usual.
I have the same problem (pidgin 2.10.3 on mint 13 with unity and backport). I can also make pidgin show up when I remove .purple/prefs.xml.
But then, the window frame (title bar with minimize, maximize and close icons, drag corners) behaves as if it weren't there.
E.g. I can't drag the pidgin window because when I click the frame, the click goes through to the window below it, or to the desktop if there is no such window.
But I can use the contents of the pidgin window as usual.