Combobox selection in firefox doesn' t work (TestComplete V11.10.1005.71)

Hi all,

Does anyone meet the problem that the combobox selection doesn't work in the firefox? The testcomplete version is 11.10.1005.71. 

Aliases.home.combo1.focus();
Aliases.home.combo1.ClickItem("A");

We got the error "A was clicked, but the selection was not changed."

Regards,

Jie