Having an issue on my Umbraco 4.5.2 instance where fields of type "Richtext editor" don't display the editor or even the textarea in the back-end.

It's running on IIS under Windows 7,

If I go to http://www.website.local/umbraco/plugins/tinymce3/tinymce3tinymceCompress.aspx, I get the following error, not sure if it has any bearing on this issue:

Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; 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: Tue, 14 Sep 2010 11:02:45 UTC


Message: 'tinyMCE' is undefined
Line: 252
Char: 1
Code: 0
URI: http://www.website.local/umbraco/editContent.aspx?id=1063

Also, loading Umbraco in IE yields the following JS error:

Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; 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: Tue, 14 Sep 2010 11:02:45 UTC


Message: 'tinyMCE' is undefined
Line: 252
Char: 1
Code: 0
URI: http://www.website.local/umbraco/editContent.aspx?id=1063

I've tried with all of the different browsers, the same thing happens. 

I had the site (4.5.2) running under VS2010 and Cassini previously, and I then did a fresh install of 4.5.2 just under IIS as normal and imported the package of content, document types, macros, xslt files, etc from the first site. I think the problem started occurring straight away on the new site.

Any ideas anyone?