I had a problem with Ajax support, next link was displayed even on last post. Here is a "fix" that worked for me :
In ple-navigation.php, function ple_navigation_placeholdervalue, around line 113, replace line :
if( count($posts)>=$args['numberposts'] )
By lines :
$nextargs = $args; $nextargs['offset']++; $nextposts = pl_getposts( $nextargs ); if (count($nextposts)>0)
Hope this helps.