Using FireFox 18 on OSx Mountain Lion MacBook Pro with Retina & second screen attached.
Using FireFox on the second screen, whenever I click for a menu to popup, the menu pops up on the main retina screen.
Same here. Current Mountain Lion 10.8.2, Firefox 18.0 Retina on macbook pro retina, second monitor is LED Cinema Display. Firefox window NOT in fullscreen (and smaller than retina full screen)
With firefox on main laptop screen, extras like suggestions from typing in URL-box appear in correct location, correct scaling. Drag firefox to 2nd monitor, firefox operations appear OK EXCEPT for said prompts.. which appear on main retina screen at some arbitrary location but 1/2-size (i.e. point sizes are for non-retina)
Dragging firefox back to main screen, back to normal good functionality.
Try to disable hardware acceleration in Firefox.
You can also check for problems with the localstore.rdf file.
Tried turning off hardware acceleration as recommended. No improvement. Leaving it turned off, and restarting firefox in safe mode, no improvement.
I have been using this config of monitors with previous Firefox 16, 17 etc.. just goes wrong since 18.0