I am in the main fork (77.69% participation) try to remove the chain directory (~/.BitShares/chain/) and change the checkpoints.json in this way (added a recent block in main chain) and restart the client:
[[
2117977,
"1f9cdf643f1e21af79a18fe35751cd1593252014"
],[
2104000,
"147f68b04701f176cab47a512430c9a82c78e217"
],[
2071001,
"58847f93f0d1846cb9250d7ba342bebda6e698e4"
],[
991701,
"2e48f0a16d2107b9ab3d1c87e803ee70d3c91ce0"
],[
640001,
"11c748cdbfc445396deb6d24908521701aaa80aa"
],[
820201,
"904278b4bd585e3055c092aada1e030fbdf69a0e"
],[
613201,
"3317ea0a272976a10ef6593e840f9ff2032affad"
],[
1315315,
"baede744122d4b8d296ab3497bf5c849d1131466"
],[
871001,
"137ee1e9171a7ed1fe9cc58536d8e20749c3f199"
],[
578901,
"add6131c7bc6f1c9470de209b0e9c257d664f1c9"
],[
494001,
"59836f51f13e07be1de734a02360742c7b5f0dd6"
],[
451501,
"42e519db48f09570fcc02f38288648a92789dcb3"
],[
554801,
"4a992cc282a0024d393c6389cf84cbb8df1fc839"
],[
408751,
"12481e818abe9bc86069e45586df11d2cff7dbb8"
],[
357001,
"d240848ca9bf4be30204eded02fb35ce2e215d41"
],[
340001,
"d3858436100abe3ad7ee9f026e5f7f4781732e06"
],[
1772201,
"5832516564d86e86edbbb501cabec98c77504307"
],[
316002,
"206b7e6574019f4352515bd3d96162fb40a1b18a"
],[
274001,
"f46c109cfb1bac323122ae59b08edc23328d880c"
],[
1575501,
"52c5e5764fba4c876cde8c80e598c89ee5c35d9f"
],[
1,
"8abcfb93c52f999e3ef5288c4f837f4f15af5521"
]
]