I love your gallery and I am using, but tweaked the jquery plugin in a couple of spots.
Firstly there is an issue with the code in method:_checkPosition()
The unbind for the next arrows does remove the click event, however this allows browsers to go to default behavior for onclick event, where when the href="#" will cause an onload in some browsers. So you need to bind an onclick event that returns false to override default behavior.
I changed 2 lines of code from:
$pp_pic_holder.find('a.pp_arrow_next').addClass('disabled').unbind('click'); //line 428
$pp_pic_holder.find('a.pp_arrow_previous').addClass('disabled').unbind('click'); //line 440
Next...you cannot by default run the jquery "prettyPhoto" extension more than 1 time...I load some ajax and wanted the ability to run this after specific areas of the page had loaded. To fix this, just need to comment out line 85.
//$pp_pic_holder, $ppt, $pp_overlay, //removed because otherwise cannot run multiple scripts
Truthfully not sure why this makes it all work, but it did. Just tried it as the error I was getting involved the $ppt variable.
Otherwise great script....thanks a bunch for the great work.