Some sounds don't work in Logic for me

Hi. I'm running Logic 9 on a 2010 13 inch MacBook Pro 2.4 ghz 4 GB OSX 10.6.7. Logic works perfect for me except that every now and then a few select sounds do not work. In fact, they do not load and cause my Logic to freeze and crash. It is very frustrating because the sounds that do not work are dispersed randomly and I forget which one not to click and then my entire project is lost. I can give you some of the sounds that I know off the top of my head that cause logic to crash: Orchestra>Choir>Chamber Ensemble, Gregorian Ensemble. I noticed this folder around half don't work and then other folders 1 or 2 sounds don't work. I would say that it's only about 1% of the entire library.

I'm pretty sure it is not a memory problem because the files selected are no bigger than other files I select. I thought that the files might have been corrupted somehow, so I actually reinstalled Logic 3 times, but I get the same problem. I downloaded all the updates. I also checked my hard drive and there are no problems with it. My only guess is that somehow the discs I bought did not get manufactured 100% correctly and some files did not get burned on properly. I don't see how only a few select files wouldn't work, but I had bought some blu-rays before where it would freeze at a certain section and I exchanged it for a working copy. Anyone have any leads or suggestions?

Thanks in advance,

Richard