So is you reader unusable? The Sony site has an update to the PRS 600 for the MAC - Version: 1.0.01.08040 (I don't know if the periods being in different spots means anything.) Of course it says its for the 600 only, but if you can't get you reader to work.... The link is
http://esupport.sony.com/US/perl/swu...=4800&os_id=99
I don't recommend this if your reader is working! I don't know the differences between the 505 and the 600. I have never used a MAC and I am not a very technical person. I don't even know if you can downgrade. Maybe someone else will come along and help you determine if it is safe to use this download.
Otherwise, maybe you have a friend with a Windows PC that can help you out or a library in your area that has computers for use.