The Image Manager Extended has been updated to fix some issues introduced with the change to the WideImage library added in 1.5.6. PHPThumb is used by default, with PHP5 issues in this library fixed, but an option exists to use WideImage if necessary.
In addition to this, errors caused by insufficient PHP memory when creating preview images or thumbnail images in the browser list have been addressed. A preview image or thumbnail image should always load regardless of whether a cache thumbnail could be created or not.
UPDATE
1.5.7.2 has been released which improves the creation / display of list and preview thumbnails. The JCE Utilities option / label in the Popup tab has also been replaced with JCE MediaBox, and the Browser List pagination selection set to 'all' by default (this option will be globally set for all relevant plugins in the next JCE Editor update).
UPDATE
1.5.7.3 has been released to fix a small bug that prevented thumbnails being shown on some systems.