RMagick trouble?

Hello,
I'm having some trouble with opening files with ImageMagick, by way of RMagick. When trying to open an existing image, I get this error:
"Corrupt JPEG data: premature end of data segment: "

My code is pretty straightforward:
pic = Magick::Image.read(filename)

I can view the image in question through the browser, so I don't think it's corrupt. Any ideas?

Thanks,
Doug