This seemed to happen on a clean load of "The Word" minimal install (that only installs one bible).
If you click "Compare" it appears to do nothing or just switch translations because there is only one bible selected. It would be great if:
a) users were blocked from picking ONLY ONE bible in the selection interface
b) having only one selected (however it happened) is detected and the "select bibles texts" for compare view screen is presented (same as when none are selected.)
D.