There are several free players like
cog,
Play and I believe even winamp is now available for the mac.
The most likely reasons you have duplicates in your library would be a) you actually have the files in two different locations on your computer, b) you have imported your library and/or that song twice.
I would recommend reviewing the "information" pop-up for the duplicated songs to see what is going on. You will have this same issue with any media manager out there so you will have to address this for how you see fit. There is an option to display duplicates in iTunes which will help narrow down the issues.
I'm not getting any crashes, but if you are close to an Apple Store and can recreate the problem, take it in and ask. Another option is to back up your files, and rebuild your iTunes library (several examples on the web).
Also consider having iTunes consolidate your library before you rebuild your iTunes library. This won't remove any files, but will copy all songs to a single location with a pretty reasonable directory structure which you can then browse and review.
