By Chance do the files that will not play come under any of the following situations :
o They are audio books
o They were purachased with iTunes 4.5
o They were purchsed and played on a diiffernt PC that you are playing them on with VLC
None are audiobooks. Some were purchased with iTunes 4.5 and some were purchased on a different PC, but others were purchased under iTunes 4.2 on THIS computer.
However, inspired by your comment, I took a more careful look at the files. I had thought that some of the files were newer and some were older, but that is not the case. Every file purchased before May 14 works and every file purchased on or after that date does not.
Inspired by JonLech's post, I took a look at my iSCInfo files. The iSCInfo2 file has not been modified since May 22 while iSCInfo was modified today. From what I can see in the code, VLC is only using the iSCInfo2 file. I modified the code to use the iSCInfo file instead, and sure enough it worked! So it seems that all of my keys are in iSCInfo but only some are in iSCInfo2. Strange.
I'll forward the information to you, JonLech.