Adding the following lines to my /etc/environment file, along with installing ibus-qt and running qtconfig to set the default input method, allows Skype and Ibus to work together on my Arch 64-bit system running Gnome 3.2..
LANG="en_US.UTF-8"
LC_ALL="en_US.UTF-8"
GTK_IM_MODULE=ibus
XMODIFIERS=@im=ibus
QT_IM_MODULE=ibus