I gave up on the issue and tried a different approach. Used another uploader (pluploader) and could upload a 4 GB file just fine.
For more info see my other post: Enable PLupload
One thing though: I think the issue could have been related to chunking. Pluploader allows setting the chunk size. If you left this field empty, it will crash just like before, because it will just use the biggest chunksize possible. If you set it to 2mb however, it works like a charm. So maybe if one could enable chunking with the standard uploader, the issue might be resolved.
Sincerly N1gh1ow1