Filesystem won't mount because of "unsupported optional features (80)"

[Maurice Volaski]

I made a filesystem (mke2fs -j) on a logical volume under kernel 
2.6.20 on a 64-bit based system, and when I try to mount it, ext3 
complains with

EXT3-fs: dm-1: couldn't mount because of unsupported optional features (80).

I first thought I just forgot to make the filesystem, so I remade it 
and the error is still present. I ran fsck on this freshly made 
filesystem, and it completed with no errors.

------------------------------------
Here's the dumpe2fs -h info:
dumpe2fs 1.39 (29-May-2006)
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem UUID:          a4b7ee96-4aa9-4312-9ec9-91059539ece5
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal resize_inode dir_index filetype 
64bit sparse_super large_file
Default mount options:    (none)
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              393216000
Block count:              786432000
Reserved block count:     39321600
Free blocks:              774032395
Free inodes:              393215989
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      1024
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         16384
Inode blocks per group:   512
Filesystem created:       Fri Feb 16 20:00:51 2007
Last mount time:          n/a
Last write time:          Fri Feb 16 20:36:07 2007
Mount count:              0
Maximum mount count:      23
Last checked:             Fri Feb 16 20:36:07 2007
Check interval:           15552000 (6 months)
Next check after:         Wed Aug 15 21:36:07 2007
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:               128
Journal inode:            8
Default directory hash:   tea
Directory Hash Seed:      a00b379c-0028-4659-93e8-b0a9198ed6c0
Journal backup:           inode blocks
Journal size:             128M
------------------------------------

Here's the lvdisplay output on the logical volume:
--- Logical volume ---
   LV Name                /dev/vgw/lvhall
   VG Name                vgw
   LV UUID                eq696g-YyLS-xkwV-XGQf-ri1i-4bTK-RaN5s3
   LV Write Access        read/write
   LV Status              available
   # open                 0
   LV Size                2.93 TB
   Current LE             768000
   Segments               2
   Allocation             inherit
   Read ahead sectors     0
   Block device           254:1



What could be causing this error and what does "80" refer to?
-- 

Maurice Volaski, mvolaski at aecom.yu.edu
Computing Support, Rose F. Kennedy Center
Albert Einstein College of Medicine of Yeshiva University