Recapcha giving error on IE8 browser.

Hi friends, I have used Recaptcha on my ASP .Net 4.0 web form. when i clicke on recapcha Refresh button for new chalenge it's giving me error like this. "htmlfile: Can't move focus to the control because it is invisible, not enabled, or of a type that does not accept the focus." This error comes in IE8 browser only. it works fine on Google Chrome & Mozilla Firefox. plz, helped me out.