Zoho Sheet Remote API Error

Hi there,

i am using the remote sheet api with a normal form submit in order to edit sheets in zooh sheet and to save it to the given saveurl.
anyway, i am always running into the same error when i'm trying to post the following link with the given form params (without linebreaks of course)

http://sheet.zoho.com/remotedoc.im?output=editor
&apikey=12345678
&url=http://foobar/test.xls
&filename=test.xls
&saveurl=http://foobar/extupload
&id=123
&format=xls

after the call of that link i can see the zoho sheet editor but with an error message called:
Error occured

and a Back link. How can i avoid this error and let my remote xls sheet be shown in zoho sheet?

Thanks in advance...