zeevm.co.il on "comments not threated right after wordpress upgrade"

this problem is happening on the default theme as well !

when i add a "reply" to a comment it is going to the bottom, in death -1, insded of to be threaded under the comment it is replayed to.

see here:
http://chinchilot.com/%D7%A9%D7%90%D7%9C%D7%95%D7%AA-%D7%95%D7%AA%D7%A9%D7%95%D7%91%D7%95%D7%AA-%D7%91%D7%A0%D7%95%D7%A9%D7%90-%D7%A6-%D7%99%D7%A0%D7%A6-%D7%99%D7%9C%D7%94/

any ideas ?