Using the Seagate FreeAgent Desk for Mac on PCs
If it's formated FAT-32 with MBR based partition scheme, pretty much every OS out there should be able to read it without any trouble or 3rd party drivers.

The only downside is FAT-32 does not support files over ~4.2GB. If that's a problem, I would suggest NTFS. This requires a additional driver (NTFS3G) to write files (NTFS works read-only on OS X only), but is supported on pretty much every platform out there as well (Windows, Linux, Android, Mac OS X, FreeBSD, NetBSD, OpenSolaris, QNX, Haiku, and more...).

The GUID partition scheme is much more recent then MBR based partition maps, so it is not as widely supported. Everything should support MBR. If you're Ok with just Win Vista/7, OS X, and any recent Linux Distro, the GUID partition scheme should also work.



It's worth noting that the issue with listing files you mention in the question is very strange. It sounds to me like a corrupt volume on the drive (E.g. a bad drive, or someone yanked the power in the midst of a write, and something got corrupted). I have had many external drives (15+), and never had any issues with the underlying USB system that weren't fixed by just disconnecting/reconnecting the cable.

The USB Mass-Storage device class protocol is extremely well understood, documented and tested, and having a device implement it improperly (Particularly from a company as large as Seagate) at this point is vanishingly unlikely.