I've found bug in table fields popups. CMS popup form is added to page as iframe. Frame code has own head part, but doesn't have meata tags, especially encoding. In IE this code causes that new values are truncated starting from position of first national letter (in my case polish letters). This bug doesn't occur for first added value, only for next (when popup content is reloaded by ajax and user is adding next value).
To solve it I've added encoding meta tag to ComplexTableField_popup.ss. Is better way to solve this bug?