Reducing LVM: Volume Group/ Physical Volume

[SL6-A1000]

Hi,
I currently have installed an LVM over a whole 1TB hard drive but i would like to reduce the volume group from 1TB to 650GB. I don't want to really reinstall because there is a lot of information on the OS and a lot of custom installations that weren't in the repositories or included during install, so it really isn't an option.

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My Disklayout is somewhat complex and probably unusual, but here it is:

sda: Linux MBR (Grub V0.97) (1GB), Linux Root (20GB), & Grub 2 (1GB)
sdb: Linux LVM

LVM Partitions:
Used-space: 469GB of 1TB (i.e. physical extents)
Logical Volumes: (in no particular order)
home (200GB)
usr (200GB)
swap (14GB)
tmp (5GB)
work_files (50GB)
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I will be resizing it in single-user mode to reduce errors and other problems.

This is the following command i used to reduce the LVM but it appears to have done nothing.

lvm pvresize /dev/sdb1 --setphysicalvolumesize 650g

it comes up with physical volume has been changed but 0 changes occurred. OR something weird.

Can i get some help with what else i need to do?

Thanks

[SL6-A1000]

bump!

Can i please get some help?? I have already done the first step of resizing the physical volume, but nothing happened.

Do i need to use the pv name instead of "/dev/sdb1"???