Thank you for providing the link to your gallery.
I have viewed your gallery in Chrome 36.0, Firefox 31.0, Internet Explorer 11, Opera 23.0 and Safari 5.1.7 (PC) and do not see the problem you report.
So far, we know that the problem happens in Safari on Mac. Do you see the problem in other WebKit browsers on your Mac: Chrome and/or Opera?
Also, you have narrowed the problem down to the use of imageTransitionType="CROSS_FADE".
First of all, try using just imageTransitionType="CROSS_FADE" as the only option in your gallery's XML file to see if this, by itself, is enough to cause the problem.
If the problem does not happen when using only imageTransitionType="CROSS_FADE", then try to narrow the problem down further by reducing the number of configuration options in your gallery's XML file until the problem no longer exists. (Try changing the values of imageTransitionTime and displayTime before removing any options to see if this makes a difference.)
Unfortunately, as I am unable to see the problem in your gallery and cannot replicate the issue in a test gallery of my own, I am unable to try the suggestions above myself so I would appreciate your help in tracking down this issue as far as possible.
Thank you.