problem with pro-tools 6.9 and external drive

i just upgraded to tiger so i could run propellerhead reason 4. reason runs fine now when i try to open a pro-tools session i will get an occasional neo-access error message. another problem; all of my recordings are stored and run on my lacie big disk firewire drive. pro-tools gives me a message saying that this is not an audio drive. it always worked before i installed tiger. i've got projects that i need to finish. hellllllllp!