[dnanian]

It certainly sounds like a hardware issue, peepsula. We're accessing the drive at a very high level, using standard file calls. If you get a pinwheel, it means the OS itself has "blocked" trying to write to the drive (which is why it's blocked in Finder, too).

It's hard to know if it's a FireWire, enclosure or drive issue, though - but it sounds like they don't spin up properly after a spindown. Turning off "Turn off hard disk(s) when possible" in the Energy Saver preference pane might help that.

Whose enclosures are these? Have you verified their Mac compatibility and updated the firmware to the most recent version? Do they use Oxford chipsets, or the "dreaded" Prolific ones? And, is this Panther, Tiger, Jaguar...?

Sorry for the barrage of questions, but maybe some element in there will help me, or someone else on the forums, diagnose the issue and offer suggestions.