Thank you for your post.
I am unable to replicate the problem. The correct path would include forward slashes "/". That is:
Using your example:
file:/ITUNES/iTunes/Books/Drum Books/Alan Hall - Elements and Ostinatos Book 2.pdf
This works for me on both Mac OS X 10.6.8 and Mac OS X Lion, and using my own shared server.
Let me know if you continue to run into difficulty.