I think this is fairly common knowledge at this point in the podcasting game, but every now and again I run across a podcaster asking why his show sounds like it was recorded by Alvin, Calvin, and Theodore when it is played back using an embedded Flash player.
While the reasoning behind it may be arcane, the fix is simple. It has to do with the fact that the Flash player (ANY flash player) only seems to have the ability to deal with sample rates that are multiples of 11,025Hz. One day Adobe may explain this, but for now we just have to live with it.
If you have a show or two that doesn't sound right, re-encode it using a sample rate that is a multiple of 11,025. We record our shows at 22,050Hz (or 22Khz) which works fine.