Regarding the hand issue above: it may well be not an issue with the cards or the number of songs in general. But rather one song or album that the quite sloppy AK100 codecs can't read and thus add to the database, and thus appear to be crashing, or rather hanging the player... unfortunately the only way to sort that out is to start fresh and copy blocks of your total collection over, run a manual scan until you narrow it down to the offending tracks locking up the scan process...
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This player is so frustrating, probably 85% of my albums lack artwork on the player despite being verifiably embedded in the files. Recently, I added a couple of HD Tracks albums, one simply becomes "2" as the album title, the other has track names of "D", "I", "W", but only for some tracks, some are OK for the same album, and those characters are not even the first letter for those tracks' names... it's as if the AK100 uses a random character generator every time its codecs fail to decode a tag -_-
Never mind it can't handle most extended western characters, the way it mangles for example Janáček, with some characters looking like they're from a different font, if not a downright a square. Sometimes it even removes surrounding characters so Mylène becomes Myène, thought I'd made a typo, but no, the original file's tags are correct... except on the AK100... again, this would be OK on a generic imported asian media player, but on a device that touts itself as being a high-end device for the discerning audiophile, it's just sad to put it nicely.
I'm just don't have the time to babysit every single bleeping track/album I own through a sometimes multiple-attempt process to make them appear correctly on the AK100. Especially since I already spent quite a bit of time to thoroughly organize and tag them in the the first place, and didn't have any issues until the AK100.