<OT>
I found out, why my server kept interrupting the downloads! Apparently it wasn't a bug, it was a feature! My hosters had some apache plugin installed, which intentionally killed bigger downloads. The reason was, there aren't any filesharing options in my server package. Simply a web server. They kindly removed it at my request...
If I ever get my hands on these guys... I mean, what am I paying for...
</OT>