This is a well-known bug in XOOPS 2.0.16
All XOOPS>=2.0.13.2 have not this bug.
Of course, 2.0.16-JP from xoopscube.org has not this bug also.
Just 2.0.14/15/16 from xoos.org are buggy.
how to fix:
http://xoops.peak.ne.jp/md/news/index.php?page=article&storyid=354