Xpages bug: File download control in error

In an application we build, there was the need for a file upload and file download control.
Uploading works fine and the files are displayed in the file download control as you can see in the screenshot.
And in the Notes client the uploaded files are nicely displayed as attachments.

But when attempting to open the files through the file download control, the browser displays an error 500: "HTTP Server command not handled exception" and the server console displays the errors displayed below this article (1).

And the standard 8.5 discussion database produces the same error.

We did find a workaround (far from ideal and the admins nightmare), which is to place the database in the servers data root directory.
Through the PMR response by IBM, I found this was already blogged by Mark Hughes in april 2009.
The issue is solved in 8.5.1 but that doesnot help us as we will not upgrade (for several reasons) to 8.5.1 for a while yet.
I do not understand why it was picked up at the time to be solved in the future 8.5.1 and not fixed in the live release 8.5.

Software versions:
- DDE 8.5.1 on Windows XP Pro
- Domino server 8.5 FP1 on Windows 2003 server

(1) Domino server log errors:
HTTP JVM: SEVERE: CLFAD####E: Exception thrown
HTTP JVM: SEVERE: CLFAD####E: Exception occurred servicing request for: /development/uitzendkrachten.nsf/xsp/.ibmmodres/domino/OpenAttachment/Uitzendkrachten.nsf/849E2F5A666919A1C12576B600487E9A/Body/program1.JPG - HTTP Code: 500
HTTP Web Server: Command Not Handled Exception [/development/uitzendkrachten.nsf/xsp/.ibmmodres/domino/OpenAttachment/Uitzendkrachten.nsf/849E2F5A666919A1C12576B600487E9A/Body/program1.JPG]