nexus 10 cwm issues

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http://forum.xda-developers.com – just got my nexus 10 and rooted by seller. the original system is 4.1.1 when arrived. so i updated to 4.1.2 through OTA. most daily use is normal, except for one thing. i cannot boot into cwm anymore. ive tried third party apk to boot into cwm,but still not working. ansd also install cwm apk to flash cwm.i got some error message when flashing cwm. finally ,i install goo manager and install twrp,but still cant boot into twrp. anyone can help? (HowTos)