Make drop down in classifieds not working

[The Moose]

Firefox on a Mac here - the make drop down just doesn't work

[The Moose]

Before someone says just use the list below, that's all well and good, however you can't get the thing to then show all models from one manufacturer as the tick-box option on the final page doesn't appear to work properly either

[The Moose]

It worked for a while, but now isn't working again...