Calendar won't close

Greetings,

I'm running Firefox 3.0 with FarCry 5.1.6 and when I try to select a date using the calendar, it won't close.

I encountered the same problem on 5.1.1 but fixed it, although I can't remember where I made the changes. Has anyone else been able to fix this problem, and if so could they shed some light on which files should be changed? I've compared the new and old code but everything to do with the calendar looks identical.

Cheers,
-Phil