RMC is usually a solid choice. Isn't Camtasia just a screen recorder not a stream ripper?
Btw, I just noticed tonight that RMC has a format converter built in. I've never tried it so I can't tell you how good it is.
Also, you may have more luck if you reinstall the previous (v9) of flash player.
Edit: I take it back. That's no longer an issue. v10 works fine. Still it depends on the source you're ripping from.