[2008] Opening a file dynamically

Good Afternoon,

An annoying one that is bugging us:

We have a list of catagories on a website then when a catagory is selected a list of documents is picked up. Now there is also a button on the page (asp.net button)

When a document is seleceted it posts it url to the button then hitting the button should open the selected document now the majority of these documents will be word, excel or pdf.

What happens when we try: postbackurl command we get the following html error:
'The http verb is not allowed'

That is when the url is: http://www.ourdomain.com/ourdocument.doc

If we change that url to: http://www.ourdomain.com

then the listed way works perfectly. Has anyone seen or heard of this or even better know how to open a document with a button in such a way we can edit the opening url in runtime.

Thanks,
Max