Some form problem

We have a form which runs well in environment Debian ETCH with Python 2.4 and 
behave strange in Debian LENNY with Python 2.5. The problem in Debian LENNY 
with Python 2.5  is when I click on the Combobox which is connected with 
Datasource with other table then the content of the Combobox appears in some 
other fields which are from the master source and doesn't stores the value. But 
when I use Tab it works fine. And also it works fine in Debian ETCH with Python 
2.4 .
 
Thanks in advance