I'm having the same problem described in this thread and several others. I moved files created on a PC in Flash 8 to a Mac running CS3. I've tried the solutions provided here without success.
  • I've triple checked the read-only
  • I tried re-naming
  • I moved the files to a new location

It's not realistic for me to go back to the PC and there are too many Flash files to recreate completely in CS3.

Thanks for anyone willing to help!