Issues with group filter

I have a pretty simple DM based on Siebel DB - list of accounts, and for each account - list of contact. On Accounts data group i have aggregate function column that counts the number of contact in that account. It works fine. The issue starts if i try to use this aggregate as group filter - it work fine if i specify the filter as "CONT_CNT=0" the resulting XML only shows accounts with zero contact. But if i specify it as "CONT_CNT>0" then i get EMPTY XML, like that
<DATA_DS>
</DATA_DS>

Any idea what is wrong ?