The length zero issue happens whenever someone uploads a video with a bad meta map (common with .flv files and .wmv files). If the file actually uploads without problems but shows a 0:00 after converting, you can fix this by:

1. Rerunning the flvtool on the file:
Code:
flvtool2 -U convertedfile.flv
This will rebuild and overwrite the bad map.

2. Change the length in the admin panel to match the file's length.