Check Box is disappearing when placing cursor in Custom theme of SAP Portal7.3

Hi,

I have customized the standard theme  with the business required look and feel in sap Portal 7.3 and assigned to user,

But now when ever user is pplacing the mouse curser to check box, check box starts disaapearing,

When user is removing the cursor, it again  appearing.

But when i am using standard theme, its working fine

Suggestions will be appreciated

Regards,

Tarun Dhuria