Receiving "Not enough PVs with free space..." when attempting to extend striped volumes.

Issue

• when attempting to run lvextend on striped volume, receive the following error:

[root@rhel4u8 ~]\# lvextend -L +512M /dev/vg1/striped_lv  
Using stripesize of last segment 64.00 KB  
Extending logical volume striped_lv to 1.00 GB  

• Not enough PVs with free space available for parallel allocation.
  Consider --alloc anywhere if desperate.
• The logical Volume that is being extended is a striped volume and somehow there are multiple stripes are on the same disk:

    Notice: /dev/vdb1(0) and /dev/vdb1(32), /dev/vdc1(0) and /dev/vdc1(32)

[root@jagee-rhel4u8 ~]# lvs vg1 -o +devices
LV         VG   Attr   LSize   Origin Snap%  Move Log Copy%  Convert Devices
striped_lv vg1  -wi-ao 512.00M /dev/vdb1(0),/dev/vdc1(0),/dev/vdb1(32),/dev/vdc1(32)

[root@jagee-rhel4u8 ~]# lvs vg1 -o +seg_pe_ranges --segments
LV         VG   Attr   #Str Type    SSize   PE Ranges                                                   
striped_lv vg1  -wi-ao    4 striped 512.00M /dev/vdb1:0-31 /dev/vdc1:0-31 /dev/vdb1:32-63 /dev/vdc1:32-63

• There is available free space to extend the logical volume:

[root@jagee-rhel4u8 ~]# vgs vg1
VG   #PV #LV #SN Attr   VSize VFree
vg1    2   1   0 wz--n- 1.99G 1.49G