This is strange.
That page you linked renders correctly, but my example does not.
I have this version of Opera - it is a current beta:
Opera/9.50 (Windows NT 5.1; U; en)
Also in this example, when I click the Insert Image button I get this error:
Server Error in '/' Application.
Input string was not in a correct format.
Stack Trace:
[FormatException: Input string was not in a correct format.]
System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +2725283
System.Number.ParseDouble(String value, NumberStyles options, NumberFormatInfo numfmt) +113
System.Double.Parse(String s, NumberStyles style, NumberFormatInfo info) +188
System.Convert.ToDouble(String value) +68
CuteEditor.UploaderBase.get_IsBrowserSupportUploadScript() +1354
CuteEditor.UploaderBase.OnPreRender(EventArgs e) +20
System.Web.UI.Control.PreRenderRecursiveInternal() +77
System.Web.UI.Control.PreRenderRecursiveInternal() +161
System.Web.UI.Control.PreRenderRecursiveInternal() +161
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1360
But again - the page you linked does not throw this exception (in the same browser).