FCKeditor 2.5.1 crashes IE7 when editing source

Hello,

FCKeditor v2.5.1 sometimes crashes Internet Explorer 7 when you press OK after editing the HTML source, if FCKConfig.SourcePopup is set to true. I cannot reproduce the problem with FCKConfig.SourcePopup set to false, nor can I reproduce it in Firefox with either setting.

Once in a while, before crashing a javascript error message is displayed (translated from swedish):

Line: 330
Character: 1
Error: Object doesn't support this property or method
Code: 0
URL: [...]fckeditor/editor/fckdialog.html


I can provide fckconfig.js and (as far as I can see, completely valid) HTML code that causes the problem to happen, but I'd rather not post it in a public forum so drop me an e-mail.