IE issue when using default Wordpress Password Protected page

I have a site that has a password protected page created using Wordpress' default options and I've had my client tell me that they're getting an error in Internet Explorer saying this:

To display the webpage again, the web browser needs to resend the information you've previously submitted.
If you were making a purchase, you should click Cancel to avoid a duplicate transaction. Otherwise, click Retry to display the webpage again.

Any idea why this is happening? So far I've only seen it in Internet Explorer. Is this a bug with Wordpress?