ffmpeg and flv files

[Ursidae]

I'm trying to create a .jpg file using ffmpeg and a .flv file as my input.
Here's what I have:

ffmpeg -i myvideo.flv -vcodec mjpeg -an -f rawvideo -s 400x320 test.jpg

No matter what I always receive this error:
I/O error occured
Usually that means that input file is truncated and/or corrupted.

I've tried using a .mp4 file in place of the .flv file and everything works just fine. Is there a codec library I could be missing, or does my command look incorrect?

[FakeOutdoorsman]

I/O error occured
Usually that means that input file is truncated and/or corrupted.
I've only seen this error if the input file is actually corrupted. Try re-downloading it.

[Ursidae]

Putting apostrophes around the file names solved my problem.