"Not a valid picture file." for all video uploads

[Echidna]

I'm getting the "Not a valid picture file." message, while using "Add Video", for every combination of video file type and size. All the videos I'm trying to upload are valid fully functioning video files. FLV, WMV, AVI, from 1MB to 20MB. Any suggestions?

[SMFHacks]

There are two upload fields on that page.
First one is for the preview image which needs to be an image file this field is not required.

The second one is for the video file which can be any of the allowed video types.

[Echidna]

There are two upload fields on that page.
First one is for the preview image which needs to be an image file this field is not required.

The second one is for the video file which can be any of the allowed video types.

heh.

[Projump.co.uk]

I made a tutorial on how to upload vids for my forum users.
http://img407.imageshack.us/img407/1783/videogallery600up3.jpg
Steps 3 & 4 will help you.