Hiya,
This is a problem that no doubt has an embarrassingly simple solution, but it's got me stumped.
The "Export..." window has got 'stuck' above the Finder's menu bar, so it can't be used, moved or resized. See below...
I've tried restarting, rebooting, changing screen resolutions, starting PM with various key modifiers (hoping for some sort of reset) - all to no avail. Now I await the howls of laughter at my jaw-dropping stupidity!
MacBook Pro running OS 10.8.5, PM v5.0 build 15011 (54772e6).
Very many thanks.
Cheers,
Tony