Panel Form Field Type Page - Autocomplete


I have an serious problem with the autocompletion of a type: page field at a site with about 1000 pages in 5 languages.

When i enter the first letter and immediately stop typing it takes around 30 seconds to load the autocompletion list. Meanwhile the whole site, in Panel and Template, stops working!

It gets worse when i enter e.g. 5 letters at once, the whole site is not available for minutes and the field loads several autocompletion-lists with the first letter green after 30 seconds, later the first and the second green after a minute and then just gets 500 xhrs from server console prints.

And now the interesting thing: this only happens when i edit the en, ru, fr, etc. version of a page - not if i edit the de version.

Any ideas? Thanks in advance!