We believe this issue is caused by the SimpleModal jQuery plugin that the module is using. The latest version of that plugin shouldn't cause this problem. We have plans to update that in the next release of the module.
Until the new release, forcing IE8 compatability is the best workaround I can offer. The easiest way to do that would be to add the following HTML to to the page's Page Header Tags setting:
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
Hope that helps,