Transcoding Real Video to FLV - ffmpeg sub_packet_size is invalid error

I have a large number of files in Real format that I'm converting to FLV. I've used some cheap commercial products (which often are just UI for ffmpeg) which crash or have audio sync problems. I'm told ffmpeg should help, but the version I'm using (15815) fails with a "sub_packet_size is invalid" error on my source files. The new release - 0.5 - of ffmpeg has improved Real codec support, but I've not found an executable for that yet.

So, any suggestions on the best way of converting a bunch of RealVideo files to FLV, And if ffmpeg is the right tool, any ideas on what to try next?