Lighttpd dies at file download WTF?

Hi,
I just bought a nother ramnode to setup my OwnCloud, so everything is working uploaded 90MB files no problem, and download works also. When i uploaded a 300MB file, it works until i download it. When i try to do it memory fills up to 100% and everything dies.
The VPS itself has 128MB Memory, memory_limit is 80MB, post_max_size 3000MB and upload_max_filesitze to 5000MB just to let me upload big files.

Any idea?