Updated Sept 19, 2016

We have released an updated version of the ProSelect Plugin for Lightroom (version 1.8) which solves this problem (see details below). It does this (when running on Windows machines only) by loading the exported images into ProSelect in batches of 50 images at a time. This update will still fail on Windows machines if the path to your images is more than 160 characters long (see section below). In the unlikely case that you do, then you will need to reduce this length by making your folder names shorter and/or not having your files located in too many subfolders.

Original Problem

On Windows computers only, there is a limit which can effect the maximum number of images that can be exported from Lightroom at one time using the current version of the ProSelect Lightroom Plugin. This limit is determined by the requirement that the total length of all the image paths when combined with a comma in between each one must be less than approx 8100 characters.  

For example if the path to your images is something like

F:\All My Jobs\2016 sessions\Mary Jones\Original Images\EMC020203.jpg  (total of 70 characters)

The maximum number of images should be approx 8100/(70+1) = 114.

The shorter the path name to the images, the more images can be exported in one go. So by locating your images closer to the top level on your drive and/or having shorter folder names, you will be able to export more images in one go.  

We are exploring possible solutions to this problem and hope to provide a solution in an upgraded version of the plugin in the near future.

In the meantime, best to limit your images to something less than the maximum number based on the above formula or just export and import them manually.