thanks for the tip. but this did not work...
maybe the error is due to huge imagefiles they have been using for their site, and i told them to optimize them (which they say the did), but in the log it stops on this gallery-plugin, so maybe there are still some old huge images in temp/cache of the plugin which cause the error?
AJAX Loading Error
HTTP Status: 500 (Internal Server Error)
Internal status: error
XHR ReadyState: 4
Raw server response:
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator,
[email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.