Uploading files, crossdomain and flashplayer 9.0.124.0

Hi everybody,

I have done a file-uploader which the user can place to his/her web and other users can upload files through it (to our server).

All worked alright, but with the 9,0,124,0 flash player this stopped working. All I get now is error string: securitySandboxError. It seems to be related to this article.
Crossdomain.xml has been set up but it didn’t solve it (maybe I did it wrong…). Can anybody give me some advice how to solve it? Thanks in advance!

Poco