Hi,
I have the same problem with a video file but I increase the upload_max_filesize and post_max_size to 180M.
The video file is 150 MB. The values will be loaded, I proofed that with phpinfo().
I have also set the fileuploader config to 0 in $Config['k_max_upload_size'].

A 50 MB Video was uploadable without any problems.

Have anybody an idea what also can result in an unknown error?
The php error log file is nothing printing.

Cheers