The action may be performed incorrectly, because the control is not visible

Hi,

Using Win7 and IE9.

I have created a simple keyword test on the login window page, but it's throwing a warning "The action may be performed incorrectly, because the control is not visible", but it's typing data into the username and pass fields without any problems and why am I seeing warnings? How do I overcome these?

Thanks in advance.

Gopal.