External Drive & "Error Code -36" on Mac

I've been doing a lot of reading about this error code, and it's currently ocuring for me on a 500GB external hard drive I use for when I'm shooting on the road. I am on a Mac and have tried the "._" in terminal as well as repairing in disc utility, and have now — futilely — attempted to transfer in chunks and basically "by hand" to work around the error.

I have tried this hard drive on Mac OS X 10.4.11, 10.5.8, and 10.7.1 and it seems to be happening universally within each. I am posting in this forum because the only major change that I have made in what is going on this hard drive is that I recently upgraded to the Canon 5D markii and am suspicious that I may be incorrectly formatting some files. I also recently bought a mid-to-low-end 16GB CF card which was offered at a discounted price from B&H with the camera purchase.

There seem to be a lot of variables here, and it being wedding season and all I don't really have time to try to figure this out for myself. Has anyone encountered similar errors on a Mac with the new 5D and its video system? Am I doing something wrong? And is there anyway to resolve the error without consuming intense amounts of time and possbily losing clients' photos? I have one last try, which is I downloaded "Disc Warrior" but only in hopes of resolving whatever corrupted file or data remnants are probably causing the problem. Help!

Moved to a more appropriate forum (I appreciate your concern but this is a better fit here).

Can I assume that the drive is formatted as FAT? If it is, do you need to use this HD with Windows machines and Macs? If the answer is no to this last question, you might want to try formatting it as HFS+ using Disk Utility (remember, formatting deletes everything on the drive so backup the drive first). I suggest this since the "-36 problem" happens commonly with FAT formatted drives.