Brimosoft

The asynchronuos thumbnail creation introduced in version 0.16.5 created a lot of troubles on some servers. When a user uploaded many images by ftp, the server got bombarded by many requests for thumbnails. This could, in some cases, result in a very high memory usage, internal errors and wrongly created all black thumbnails or even no thumbnails at all.
In version 0.16.7, you will have an option to create cached thumbnails after the gallery page has loaded in the browser. By default this option is off.
Check this only if you are sure your server can handle the extra load.

Some users are experiencing memory issues when Lazyest Gallery is creating thumbnails or slides. This is due to a too low amount of memory that is allocated to the Buffer size for image processing. You can set higher values in the Lazyest Galley settings. The default value is 16MB. This could be too low when you have large (in pixels) images.

You might say “I’ve uploaded equally large images with WordPress’s built in image controls and not had a problem.” Well, Image resizing in WordPress allocates a very large chunk of memory so it will not fail in most cases. This is what I found in WordPress code:
// Set artificially high because GD uses uncompressed images in memory
@ini_set(′memory_limit′, ′256M′);