The microSD have nothing to do with the problem. I just want to remind you that the first boot is very long even more than 15 minutes. Anyway, the problem of not booting after flashing maybe because the partition is too small. Do not matter if you did the right partition size, Wipe the phone with Task29 and increase the partition from original, of 30MB minimum and try again.
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My Evolution: Sony Xperia Z1, HTC HD2, HTC Diamond 2, HTC HD Blackstone, Nokia 7070 Prism, Qtek 9100, Nokia 3100, Motorola T720i, Nokia 3310, Sony Ericson PF 768 (Blue)