Headers:

Antwort-Header (Answer-Header?)
Date	Wed, 01 Oct 2008 06:57:06 GMT
Server	Apache/2.2.8 (Win32) PHP/5.2.6
X-Powered-By	PHP/5.2.6
Expires	Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control	no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma	no-cache
Set-Cookie	PastVisitor=1; expires=Tue, 30-Dec-2008 06:57:06 GMT; path=/gfu/ PastMember=1; expires=Tue, 30-Dec-2008 06:57:06 GMT; path=/gfu/
Content-Length	23
Connection	close
Content-Type	text/html; charset="utf-8"
Anfrage-Header (Request-Header?)
Host	localhost:8080
User-Agent	Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.8.1.17) Gecko/20080829 Firefox/2.0.0.17
Accept	text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language	de-de,de;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding	gzip,deflate
Accept-Charset	ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive	300
Connection	close
X-Requested-With	XMLHttpRequest
X-Prototype-Version	1.4.0_rc3
Content-Type	application/x-www-form-urlencoded; charset=utf-8
Referer	http://localhost:8080/gfu/admin/
Content-Length	0
Cookie	PastVisitor=1; PastMember=1; PHPSESSID=0mbbp05ch7n2p11844cagnj400; style=basic

And the answer it shows me is still "There has been an error". Don't really know how to use this information.

EDIT: And it says "prototype.js (Line 760)"

Hi did you ever solve this? I am getting the same problem.
Thanks
MM