Dear Lord
i have been testing with several bgs to try to reproduce that bug and havent been able to reproduce it.
i think you are 100% sure how bgs works and which one are offs and which one are deffs, so the only explanation i could find is that u are using full screen mode with last version of flash player. this version has a bug and sometimes can fail or do another unexpected action. please read carefully this post on news: http://plarium.com/forum/en/stormfall-age-of-war/-news-and-announcements/24801_attention---changes-to-adobe-flash-player--2/?post=133786
it explain the bug i said. However, if you think that is a system fail, please contact Help Desk following this link. they are in better position to investigate what has happened than we here in forum.
next time try to provide a english translation cause is the official language of the forum and the answer can be given in less time.
hope you can solve ur problem with bgs
Regards