So, I have spent a little time browsing through blocks on the block chain to see if there was any patterns in the blocks that are "stuck", and there is.
I can with some confidence say that block 11649 will have the following characteristics
The coinbase transaction will have 2 output transactions of equal size
The coinbase sig will be 26-28 characters long, and the last 14 characters of the sig will be 062f503253482f
The block will not be found by either of the pools mention in OP (Crunchharder, Bitember, Miningwithus or Cloudminers)
March 17, 2014, 08:47:45 - Found after 1h 29m
Block 11352
Coinbase 02582c02700d062f503253482f
2x 545.5 output
FAvrAQn2cpYFaowSwYiJvuQrwT7PSGp4Rc
FTkUQFwLKW8mWbdks6j2p6UxDdHY49qhkx
March 17, 2014, 06:42:02 - Found after 6h 14m
Block 11303
Coinbase 02272c03fe9a00062f503253482f
2x 1340 output
F6jNAcmpdPVP4CCZWRUZXmocbj5zcjowyN
FNG4aSWm5x6Wa8tsz8hK3XJy2itQeB8fTJ
March 16, 2014, 23:09:08 - Found after 2h 3m
Block 11214
Coinbase 02cf2b0349ae00062f503253482f
2x 2051 output
FDrYFMuhDgRJjRu72EQ7aK6rsYdZMg3L94
F88MAHkFJFX1yEKnB5faMXp11EQJj1rHL5
March 16, 2014, 20:06:49 - Found after 47m
Block 11171
Coinbase 02a32b02f034062f503253482f
2x 4632 output
FQCPgk19Ayax4wg8Sjv3jeMgrmZeQYB7jD
FHPhyaH5FcN3c3csNRGxc7KYS4NQUUxUxE
March 16, 2014, 17:20:48 - Found after 1h 27m
Block 11079
Coinbase 02472b02cf3c062f503253482f
2x 1319.5 output
FBU7EV9RacSCAKmiMnsuem4WHP2u2u82nq
F79mS72WxdQjHQLpZXm2EC5hrrLc24grH3
March 16, 2014, 09:33:52 - Found after 2h 58m
Block 10870
Coinbase 02762a02737d062f503253482f
2x 2487.5 output
FBU7EV9RacSCAKmiMnsuem4WHP2u2u82nq
FJ9ihcwZ7Lcf2JuwKZ6cmoUDc3YFYxc9UC
March 15, 2014, 19:00:29 - Found after 1h 9m
Block 10436
Coinbase 02c428027e66062f503253482f
2x 2054 output
FDrYFMuhDgRJjRu72EQ7aK6rsYdZMg3L94
FJ9ihcwZ7Lcf2JuwKZ6cmoUDc3YFYxc9UC
March 15, 2014, 17:37:15 - Found after 1h 33m
Block 10406
Coinbase 02a6280390af00062f503253482f
2x 4104 output
FMf3Y9hLxsSuotSUsYqeCQyu4FQZENkGyp
FQCXJjAjEhwKgwLHyG9DxKCgLaPPz3hVAt
Coinbase sig for the latest block found by each of the pools for comparison:
11648 02802d062f503253482f04f910275308100004840f0000000d2f7374726174756d506f6f6c2f Cruncharder
11647 027f2d062f503253482f04a310275308980178fa150000000d2f7374726174756d506f6f6c2f Bitember
11646 027e2d062f503253482f041410275308f8003861490000000d2f7374726174756d506f6f6c2f Miningwithus
11644 027c2d062f503253482f04790f275308f800368fa50000000d2f7374726174756d506f6f6c2f Cloudminers
I have no idea how to interpret the information above as I have very little technical insight to the inner workings of crypto coins and how blocks are generated.
But, assuming some of the information for the next block is known to the entire network (besides transactions), may guess is there could be some parameter or information in the upcoming block that the pools are unable to process correctly, and thus we have to wait for a non-pool miner to solve the block.
Edit: Of course thekidcoin found the problem while I was typing all this up
Well , you did put some work in it , it deserves to be praised.