As an update to the previous post: I think my initial problems were due to upgrading from such an ancient version. I believe the error 138 is Roni's way of limiting usability for unregistered copies. The new version didn't recognize my antique DLL registration files, and caused all of my versions to revert to an unregistered state somehow. Once I got an updated registration package (thanks a lot for the quick save Roni!) and wiped out the old versions/plist files/etc., everything ran perfectly.
Keeping in mind that I switched up from a much earlier copy (2.0.1), I must state right off that the speed and pitch algorithms are far cleaner and smoother than previously. I've been using Amazing X for 2 1/2 years in my private lesson studio for teaching students transcription and ear training skills. I can alter speeds to suit each individual student's needs, change tuning or completely alter the key signature as needed, and even loop segments. The Karaoke mode is vastly improved as well: I can wipe out all but the slightest hints of the original soloist to create background tracks for practicing, and I can save tracks for them to use at home. I've even convinced some of my students to purchase the program for their own use (the app is available for both Mac and Windows platforms), and they're always floored by how easy it is. I just wish I'd had this tool in university; transcriptions would have gone so much faster!
Still some minor stability issues. As I mentioned, I had to wipe out all evidence of previous versions in order to get this one to work. When old code was still floating around on my harddrive, the program installed and ran, but it couldn't retain preferences; every time I started it up it acted like it was the first time, resetting to default settings and presenting the read-me file. I had run into problems with preference settings previously as well, along with issues reading from CD, but the latest install is flawless, leading me to think it was all related to the fossilized copy I had been using. Those performing a first-time installation or upgrading regularly shouldn't have the problems I did.
In closing: if you need a tool for altering speed, pitch, or eliminating leads/vocals from recordings, this is an excellent solution. I highly recommend registering for full functionality. The price is very reasonable, and remember: Roni offers lifetime upgrading (a feature I should have takien advantage of a LONG time ago). And to think that once upon a time I was going to buy Thompson Vocal Eliminator and a speed/pitch adjustable CD system. Roni saved me thousands! Keep up the great work!