After transferring a project from server A to server B, suddenly the nextgen config data disappeared. The galeries on the page itself were no longer working, instead of a slideshow there were all images displayed without a style.
Obviously one field is not transferred correctly. To solve this problem, find an entry in wp_options where option_name = ngg_options. Copy option_value from your old database and paste it to the new one. This did the trick for me.