The error:

PHP Fatal error:  Maximum execution time of 30 seconds exceeded in gallery/modules/exif/lib/exifer/makers/olympus.inc on line 81

 

The reason:

The exif have been updates with Gallery2, but the libery have not been updated.

 

The solution:

Download the newest file for olympus images here:

http://www.zenphoto.org/trac/browser/trunk/zp-core/exif/makers/olympus.php

Replace the "olympus.inc" with the new file, and everything works.

 

Source for solution:
Gallery2 forum