Webpage error details
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; InfoPath.2; .NET4.0C; .NET4.0E)
Timestamp: Tue, 18 Oct 2011 15:01:49 UTC
Message: 'b.baseURI' is null or not an object
They have IE8 with some limitations for domain users, I'm guessing it has something to do with that but can't be sure. A default installation IE8 doesn't show the error and modern browsers work as expected also.
I've now tried removing the epipersonalizedcontent-editor-button and I'm waiting for a report from the client...
The same IE8-installation that fails on their HTTPS site doesn't give any errors at demo.episerver.com when editing so one lead is that HTTPS might trigger different and problematic security settings.