I configured two encrypted volumes using a file (not a physical volume) for each one. I'm using TrueCrypt 7.1 on MacOSX Snow Leopard. Why if I close the TrueCrypt GUI without unmounting the volumes, it unmounts automatically them both without asking me anything?
I just found out that in TrueCrypt preferences there's an option to choose if TrueCrypt should unmount all volumes on quit. I disabled it and it seems to work all correctly. Too bad I run to superuser.com before watching in the most obvious place :)