problems with locale.module

We have tried every possible way, but the locale.module simply does not seem to work correctly. We have multiple languages enabled on our Drupal system and the module is doing nothing but strange things.

* First of all, the import/export does not work: things such as plural forms, etc get corrupt while exporting; import does work, but partially - some strings get parsed, some not, no matter what I select (whether Drupal should replace or add only).

* Also the localization itself does not work correctly every now and then, sometimes strings are displayed in other languages.