Many people on the WordPress.org forums have experienced an issue where they see errors on their site that say something like “memory exhausted” when they try to use a video or image plugin on their site (however, it can occur for other reasons also). In most cases this is not a coding issue with the actual plugin they are trying to use, it is an issue with their server.
Typically this error shows up on sites that are hosted as part of a shared server. In PHP there is a setting that allows the server admin to set exactly how much memory PHP can utilize for any one process. This is designed to make it difficult for one site on a shared server to overwhelm the entire server’s resources, and therefore make all of the other sites inaccessible. When it comes to image or video processing though, memory is very necessary to allow resizing or other effects to properly allow the presentation of the file. In cases where this memory issue continually occurs you will need to contact your server admin and request that they boost your memory limit enough to prevent the error from occurring. It may also be time to think about moving to your own server (especially if you are getting very popular).
If you get these memory errors using AWSOM Pixgallery, you do have some other options. In some cases reducing the number of images per gallery page may help out the situation–Do this by making the Rows and Columns setting for Thumbnails (in the Pixgallery options area) smaller so as to extend your Gallery onto multiple pages when showing your gallery. Another option is to reduce in file size the size of the images you are using in your gallery. You may not have noticed that your images were large in filesize, and lowering their size (not necessarily resolution, but re-encoding maybe at a lower .jpg quality setting) may help reduce your overall PHP memory usage (and lower your bandwidth transmission also). In many cases the memory error will only occur the first time a gallery is viewed (the first viewing of a gallery initiates the auto-thumbnail creation). If all else fails, you can contact me and I might be able to give you a few more advanced tips specific to your situation.
In any case, now you know why this mysterious error occurs and how you can work to resolve it.