Description of problem:
Volume Name: realvol
Type: Distributed-Stripe
Status: Started
Number of Bricks: 3 x 2 = 6
Transport-type: tcp
Bricks:
Brick1: dagobah:/data/export1
Brick2: dagobah:/data/export2
Brick3: dagobah:/data/export3
Brick4: dagobah:/data/export4
Brick5: dagobah:/data/export5
Brick6: dagobah:/data/export6
Options Reconfigured:
diagnostics.client-log-level: DEBUG

If the volume type is distributed-stripe with number of subvolumes for dht is 2 then mount succeeds, & if the number of subvolumes for dht is 3 then it fails.
mount command used after creating a new mount directory:
"mount -t glusterfs dagobah:realvol /root/new"

Interestingly mounting via "/usr/local/sbin/glusterfs --volfile-id=realvol --volfile-server=dagobah strmount/" succeeds. 

The volume was created using this command:
gluster volume create realvol stripe 2 dagobah:/data/export1 dagobah:/data/export2 dagobah:/data/export3 dagobah:/data/export4 dagobah:/data/export5 dagobah:/data/export6

Client debug log:
[2011-12-21 02:25:12.262610] I [glusterfsd.c:1578:main] 0-/usr/local/sbin/glusterfs: Started running /usr/local/sbin/glusterfs version 3git
[2011-12-21 02:25:12.270759] I [common-utils.c:1940:get_mem_size] 0-common-utils: Total Mem: 3889098752
[2011-12-21 02:25:12.270783] I [io-cache.c:1555:check_cache_size_ok] 0-realvol-quick-read: Max cache size is 3889098752
[2011-12-21 02:25:12.270806] D [options.c:128:xlator_option_validate_sizet] 0-realvol-io-cache: no range check required for 'option min-file-size 0'
[2011-12-21 02:25:12.270822] D [options.c:128:xlator_option_validate_sizet] 0-realvol-io-cache: no range check required for 'option max-file-size 0'
[2011-12-21 02:25:12.270855] I [common-utils.c:1940:get_mem_size] 0-common-utils: Total Mem: 3889098752
[2011-12-21 02:25:12.270868] I [io-cache.c:1555:check_cache_size_ok] 0-realvol-io-cache: Max cache size is 3889098752
[2011-12-21 02:25:12.270902] I [quota.c:2840:quota_parse_limits] 0-realvol-quota: no "limit-set" option provided
[2011-12-21 02:25:12.270918] D [options.c:915:xlator_option_init_int64] 0-realvol-quota: option timeout using set value 0
[2011-12-21 02:25:12.270933] D [options.c:128:xlator_option_validate_sizet] 0-realvol-quota: no range check required for 'option timeout 0'
[2011-12-21 02:25:12.271001] D [options.c:918:xlator_option_init_size] 0-realvol-stripe-2: option block-size using set value 256K
[2011-12-21 02:25:12.271017] E [xlator.c:393:xlator_init] 0-realvol-stripe-2: Initialization of volume 'realvol-stripe-2' failed, review your volfile again
[2011-12-21 02:25:12.271030] E [graph.c:303:glusterfs_graph_init] 0-realvol-stripe-2: initializing translator failed
[2011-12-21 02:25:12.271042] E [graph.c:492:glusterfs_graph_activate] 0-graph: init failed
[2011-12-21 02:25:12.271202] W [glusterfsd.c:783:cleanup_and_exit] (-->/usr/local/lib/libgfrpc.so.0(rpc_clnt_handle_reply+0x20e) [0x7fd20e7e29c6] (-->/usr/local/sbin/glusterfs(mgmt_getspec_cbk+0x344) [0x40afb8] (-->/usr/local/sbin/glusterfs(glusterfs_process_volfp+0x1cd) [0x407a46]))) 0-: received signum (0), shutting down
[2011-12-21 02:25:12.271224] D [glusterfsd-mgmt.c:1498:glusterfs_mgmt_pmap_signout] 0-fsd-mgmt: portmapper signout arguments not given
[2011-12-21 02:25:12.271244] I [fuse-bridge.c:4054:fini] 0-fuse: Unmounting 'new'.

How reproducible:
Intermittently reproducible.

client volfile:
volume realvol-client-0
    type protocol/client
    option remote-host dagobah
    option remote-subvolume /data/export1
    option transport-type tcp
end-volume

volume realvol-client-1
    type protocol/client
    option remote-host dagobah
    option remote-subvolume /data/export2
    option transport-type tcp
end-volume

volume realvol-client-2
    type protocol/client
    option remote-host dagobah
    option remote-subvolume /data/export3
    option transport-type tcp
end-volume

volume realvol-client-3
    type protocol/client
    option remote-host dagobah
    option remote-subvolume /data/export4
    option transport-type tcp
end-volume

volume realvol-client-4
    type protocol/client
    option remote-host dagobah
    option remote-subvolume /data/export5
    option transport-type tcp
end-volume

volume realvol-client-5
    type protocol/client
    option remote-host dagobah
    option remote-subvolume /data/export6
    option transport-type tcp
end-volume

volume realvol-stripe-0
    type cluster/stripe
    subvolumes realvol-client-0 realvol-client-1
end-volume

volume realvol-stripe-1
    type cluster/stripe
    subvolumes realvol-client-2 realvol-client-3
end-volume

volume realvol-stripe-2
    type cluster/stripe
    subvolumes realvol-client-4 realvol-client-5
end-volume

volume realvol-dht
    type cluster/distribute
    subvolumes realvol-stripe-0 realvol-stripe-1 realvol-stripe-2
end-volume

volume realvol-write-behind
    type performance/write-behind
    subvolumes realvol-dht
end-volume

volume realvol-read-ahead
    type performance/read-ahead
    subvolumes realvol-write-behind
end-volume

volume realvol-io-cache
    type performance/io-cache
    subvolumes realvol-read-ahead
end-volume

volume realvol-quick-read
    type performance/quick-read
    subvolumes realvol-io-cache
end-volume

volume realvol-stat-prefetch
    type performance/stat-prefetch
    subvolumes realvol-quick-read
end-volume

volume realvol
    type debug/io-stats
    option log-level DEBUG
    option latency-measurement off
    option count-fop-hits off
    subvolumes realvol-stat-prefetch
end-volume

P.S: This does not happen everytime, but it happened many times & so logging it because i saw it happening & so that its recorded.