I wrote a pureperl jpeg to swf converter ages ago, archived in perpituity by google, bless 'em:

http://groups.google.com/group/macromedia.flash/msg/bee439ab6d748cbe?hl=en&

Works fine for 95%+ of jpegs, and should pick up and try and fix (using djpeg/cjpeg) any ones it doesn't like.

Note that newer flash players can read jpegs directly.

HTH,
--
Adam