Pro Tools 5.1 uses the Apple Navigational Services for opening new sessions, importing audio files, etc. This new dialogue, designed by Apple Computers, takes an unusually long amount of time to search Network Drive directories for all available files and folders (on the order of 30 seconds for 100 folders. I'm sure this is also dependent on Ethernet speeds and other network configurations). This performance seems to be the same for all applications which use the Nav Services.