This sounds like a drive format or set-up issue - as far as I am aware the Mac OS, like Windows, ignores case by default though it can be set not to as a user option. Did you turn case-sensitivity on for the external HD, and if so do you need it? DIM doesn't handle large volumes of data, so it doesn't need a 64 bit version. 32 bit software runs on 64 bit OSes, it's the reverse that not possible.