client stop sync blocks at 23:46:00 , here is the message when this happened.
received a block with invalid sign
20140702T234600.476280 th_a handle_message ] CLIENT: just received block d4908ed79c8cca84c26c4ef0ead903377fb20473 client.cpp:891
20140702T234600.476360 th_a on_new_block ] Received a new block from the p2p network, current head block is 6059, new block is {"previous":"fba6a332aa0b14467fd384ada0a8db9242a6f275","block_num":6060,"fee_rate":1000,"delegate_pay_rate":83292,"timestamp":"20140702T234600","transaction_digest":"c8cf12fe3180ed901a58a0697a522f1217de72d04529bd255627a4ad6164f0f0","next_secret_hash":"977164c0085c8f6e4c9dedd95347f7b917abe86e","previous_secret":"1a990f6be14faf8e0b25c96accf531aae6aa2812","delegate_signature":"1f3cee95de04b6713bc2319054a6d2b79613f4245b67495f2658523c0b3c65da1a63c36cae49d0d37a3b414bd0f28e4ad0f9071cc7778b783d973d0f4ae3bc461f","user_transactions":[]}, current head block is 6059 client.cpp:801
20140702T234600.476573 th_a store_and_index ] we already know about its previous: fba6a332aa0b14467fd384ada0a8db9242a6f275 chain_database.cpp:408
20140702T234600.478033 th_a apply_transactions ] Applying transactions from block: 6060 chain_database.cpp:502
20140702T234600.480006 th_a on_new_block ] After push_block, current head block is 6060 client.cpp:817
20140702T234615.479492 th_a handle_message ] CLIENT: just received block 47d84601c497133e63b1ccac86d70bc59bcc3f85 client.cpp:891
20140702T234615.479573 th_a on_new_block ] Received a new block from the p2p network, current head block is 6060, new block is {"previous":"d4908ed79c8cca84c26c4ef0ead903377fb20473","block_num":6061,"fee_rate":1000,"delegate_pay_rate":83277,"timestamp":"20140702T234615","transaction_digest":"c8cf12fe3180ed901a58a0697a522f1217de72d04529bd255627a4ad6164f0f0","next_secret_hash":"55fbf3a9fe6dd0d3aa277127d44c5b6f92c5652a","previous_secret":"bf8fc763de5712b1cc1ac761a4bc57abc8b11210","delegate_signature":"1fca2e45f2f352e7690e841bed9d5900f68748ba13151c1153a34cd529075ed746e7c1975609be8a28b0d661b22f06f9818dec028d6cdbc40407c976d3c5658f8d","user_transactions":[]}, current head block is 6060 client.cpp:801
20140702T234615.479768 th_a store_and_index ] we already know about its previous: d4908ed79c8cca84c26c4ef0ead903377fb20473 chain_database.cpp:408
20140702T234615.482675 th_a extend_chain ] error applying block: 30021 invalid_delegate_signee: invalid delegate signee
then switch fork out of control, these messages happen again and again, never switch to the main chain.
20140702T234645.494907 th_a handle_message ] CLIENT: just received block a1655804f29e7aec0c016434a2cb6c8fad7d3514 client.cpp:891
20140702T234645.494990 th_a on_new_block ] Received a new block from the p2p network, current head block is 6060, new block is {"previous":"47d84601c497133e63b1ccac86d70bc59bcc3f85","block_num":6062,"fee_rate":1000,"delegate_pay_rate":83262,"timestamp":"20140702T234645","transaction_digest":"c8cf12fe3180ed901a58a0697a522f1217de72d04529bd255627a4ad6164f0f0","next_secret_hash":"7e8c09519baed6dde4fd3e338b63e06d2f725159","previous_secret":"2dd6dd72ce38d4da157cd9c553064dc3497852a0","delegate_signature":"1f4c7637ab1c2499de927c158431e9a3edc8d3c6fcdccfe8523c84e3caa9ca5cee2843831d0c5a6af43b4f2b903cd4e018fcc41055114db4df3dc6e7b230175a23","user_transactions":[]}, current head block is 6060 client.cpp:801
20140702T234645.495203 th_a store_and_index ] we already know about its previous: 47d84601c497133e63b1ccac86d70bc59bcc3f85 chain_database.cpp:408
20140702T234645.495390 th_a switch_to_fork ] switch from fork d4908ed79c8cca84c26c4ef0ead903377fb20473 to a1655804f29e7aec0c016434a2cb6c8fad7d3514 chain_database.cpp:482
20140702T234645.495428 th_a get_fork_history ] chain_database.cpp:796
20140702T234645.495463 th_a get_fork_history ] return: ["a1655804f29e7aec0c016434a2cb6c8fad7d3514","47d84601c497133e63b1ccac86d70bc59bcc3f85","d4908ed79c8cca84c26c4ef0ead903377fb20473"] chain_database.cpp:817
20140702T234645.495501 th_a switch_to_fork ] extend 47d84601c497133e63b1ccac86d70bc59bcc3f85 chain_database.cpp:492
20140702T234645.496384 th_a extend_chain ] error applying block: 30021 invalid_delegate_signee: invalid delegate signee