"Insert Date and Time" malfunctioning

I used to insert today's date by a shortcut i defined from system preferences for iWork applications for Insert>Date and Time function. After Mountain Lion upgrade, numbers' "Insert>Date and Time" function started changing the date to 31.12.1999 in cells formatted as "Date and Time" when i change focus. Function works as intented if the cell is not formatted as "Date and Time".

Here is what happens;

http://www.evreninanc.com/Screen%20Recorded2012-08-24%2008_56_33.mov