Linux Mint 17.2: Total Crash Changing Themes

Started to have problems while trying to use or change different themes on my Linux Mint 17.2 setup.
If I open the Appearance setting program, it automatically closes after a couple of seconds with the error message:

$ xfce4-appearance-settings
GLib (gthread-posix.c): Unexpected error from C library during 'malloc': Cannot allocate memory.  Aborting.
Aborted

$ xfce4-appearance-settings
(xfce4-appearance-settings:12260): GLib-ERROR **: /build/buildd/glib2.0-2.40.2/./glib/gmem.c:133: failed to allocate 2048 bytes
Trace/breakpoint trap

If I try to do it thru the Settings manager, it simple closes the whole thing when I select the Appearance icon.

The only option to change themes at the moment is executing the command posted above, but thru sudo:

$ sudo xfce4-appearance-settings

And then logout and back in to see the changes, a total and complete PITA...