I'm having trouble copying some files from my mac to an external hard drive: I keep getting the nondescript "error code -41".

I noticed some of the files with an additional "@" permission bit had the "com.apple.quarantine" flag set. I used the "xattr" command from this article

What should I do about com.apple.quarantine?

to take care of the quarantine flag and sort that out (these files were copied over from another mac on my network, so I guess OS X flagged them as quarantine).

That took care of the problem for those files but I still have some that I can't manually copy over to the external drive. The only other thing I've noticed is that some of these files have a an extra permission bit: "drwxr-xr-x+" which I haven't been successful in googling. Aside from that I don't see anything else. Also, Disk Utility says everything's fine.

Any help would be greatly appreciated.