MaskedEditExtender error

Hi.

I have this code

<asp:MaskedEditExtender runat="server" TargetControlID="tb_time" ID="meeHoraChegada"
     MaskType="Time" Mask="99:99" AutoComplete="false"></asp:MaskedEditExtender><asp:MaskedEditValidator ID="MaskedEditValidator2"  runat="server"
     ControlExtender="meeHoraChegada" ControlToValidate="tb_time"
     IsValidEmpty="True"
     InvalidValueMessage="The Time is not valid!"> </asp:MaskedEditValidator> 

When i start to enter the time, where i press a key it fill's the hour with the twice os the key value and in the next key press i get the same number twice.

For example i press 1 the hour stays with 11 and where i press the second digit value 3 i get 33 the result will be 11:33....

if i press 2 and 5 i get 22:55...

Any idea?