Absolutely... we do it all the time. Sometimes we'll off-load the cards to a PC laptop in the field, and then transfer the files to the Apple. Sometime we'll load the files directly to the G5 and FCP.
When you offload to the PC, you're putting those clips into an NTSF formatted hard drive. Are you using ntsf on the Apple? I need to offload to a MAC formatted hard drive, not NTSF.
If you are using NTSF to Mac format, please give details.