JS error on calling Javascript methods with IE7 browser.

Hi,
Basically I have qa weird problem, In my application we are using JavaScript. As it sometimes very usefull to use JS on web application.
So the requirement is that I have to to fill up some dropdown list box (name B) on the selection of value from the other dropdown list box (name A). To do this, I have written a simple JS method on change event of dropdown box of A, to fill up with the required values in dropdown box B.
This functionality is working fine with all the MS IE browsers, but only with MS IE7 I am getting the JS errors on the page. Seems HTML is not able to underdstad the JS in MS IE7.

Any help or suggestions are welcome. Please help.

Regards,
Guest_Chin