[linux-lvm] Why can't I extend a LV after many times extends?

[lepton]

LVM version:     2.00.08 (2003-11-14)
Library version: 1.00.07-ioctl (2003-11-21)
Driver version:  4.0.0

I am using linux kernel 2.6.3

For making my data can balance on all of my three scsi disk, I use such
methods to create my LV:
  lvcreate -l 32 -n test vg /dev/sda1
  lvextend -l +32 /dev/vg/test /dev/sdb1
  lvextend -l +32 /dev/vg/test /dev/sdc1
  lvextend -l +32 /dev/vg/test /dev/sda1
  ......

  (I use a shell script to do these)

But When I extend a Logic Volumn to 26.5G, it saids:
....
  Logical volume boards successfully resized
  Extending logical volume boards to 26.75 GB
  VG amd64 metadata writing failed
  Extending logical volume boards to 26.75 GB

  (lvextend using sdb1 and sdc1 will fail, but lvextend using sda1 will
  sucess)

It is strange I have three scsi disk which are the same.

vgdisplay   
  --- Volume group ---
  VG Name               amd64
  System ID             
  Format                lvm2
  Metadata Areas        3
  Metadata Sequence No  1585
  VG Access             read/write
  VG Status             resizable
  MAX LV                255
  Cur LV                8
  Open LV               0
  Max PV                255
  Cur PV                3
  Act PV                3
  VG Size               102.54 GB
  PE Size               4.00 MB
  Total PE              26250
  Alloc PE / Size       20032 / 78.25 GB
  Free  PE / Size       6218 / 24.29 GB
  VG UUID               RSR1JG-3vRE-4esH-m8dI-rY4B-WG0p-XweADh

pvdisplay /dev/sda1
  --- Physical volume ---
  PV Name               /dev/sda1
  VG Name               amd64
  PV Size               34.18 GB / not usable 0   
  Allocatable           yes 
  PE Size (KByte)       4096
  Total PE              8750
  Free PE               2286
  Allocated PE          6464
  PV UUID               YAKwOe-oJlA-CbzF-5IwO-ReqH-JZiw-LdhtT7
   
pvdisplay /dev/sdb1 
  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               amd64
  PV Size               34.18 GB / not usable 0   
  Allocatable           yes 
  PE Size (KByte)       4096
  Total PE              8750
  Free PE               1966
  Allocated PE          6784
  PV UUID               FkVeuL-7JAW-UurK-GFcZ-e642-inMT-5MYYMq

 pvdisplay /dev/sdc1
  --- Physical volume ---
  PV Name               /dev/sdc1
  VG Name               amd64
  PV Size               34.18 GB / not usable 0   
  Allocatable           yes 
  PE Size (KByte)       4096
  Total PE              8750
  Free PE               1966
  Allocated PE          6784
  PV UUID               sRSor7-r4KP-1PNr-nESn-sZPS-aKMx-7s3CU