No problem with the couple of tracks I listened to.

Since you indicated that you'd done some "conversions" you probably have a sound editing program, and may be using it as your default for playback. Maybe MySpace just doesn't like "sophisticated" and a simpler default player sounds better(?).

Some sites like MySpace "condense" the files you upload to a standard - usually lower - resolution to save bandwidth on the server, so what comes back isn't necessarily at the same kbps that you sent. I don't know that MySpace does this, but it seems fairly likely that they do. If you're trying to force it to play back at the original quality when the incoming is at something different it might produce some noise(?).

[Our experts will be along to tell me I don't know what I'm talking about, and will be perfectly correct when they do. I don't do that much audio stuff.]

John