I've recently updated IE with the latest security patch, the version is now 8.7601.17514. Afterwards the modalPanel is no longer displaying.
The error is:
Webpage error details
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E) Timestamp: Mon, 13 Jan 2014 16:16:07 UTC