My new Western Digital Green 2TB (WDC WD20 EARS-00MVWB0) drives have 4k sectors, but they report as 512 byte for compatibility. Linux 2.6.32 and the fdisk on squeeze will do the wrong thing by default and place partitions on bad boundaries.
fdisk -b 4096 -u /dev/XXXX
… is the right command to force the proper sector size. It will then die with a floating point exception unless you type a ‘c’ to disable MS-DOS compatibility mode once you are in fdisk.
(If you are just going to use them with LVM, maybe skip the silly label anyway and use the whole disk for LVM. Be careful though, currently on squeeze the lvm scan does not happen after the USB scan, so they won’t be found at reboot unless you do another scan, like in rc.local.)