It looks like this Problem is fixed in dia 0.95. I have no longer this Problem and on the dia homepage stand "Many i18n problems have been fixed, particularly in export filters." in the changelog.
-- Export to pstricks does not work if locale has wrong separator https://launchpad.net/bugs/49386 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
