It seems like there must be something wrong with my card now. It was brand new Lexar 1000x 32gb. I recorded about 10 1920x1080 raw clips on it with no problem...usually about 3 at a time after which I would delete the files but not reformat or anything. Then it stopped working. Now it will write 116.1mb before the buffer fills. This is regardless of what resolution I try. ML shows a write speed of 6.6mb/s, so something has crippled the card. Just for the heck of it, I tried one of my older Lexar 400x 16gb cards and ML is able to write to them at 26mb/s no problem, so it's not the camera.
I've tried reformating, aligning partition to 4096, completely overwriting the card. Still, no change from 6.6mb/s. Does this sound familiar to anyone? I'm thinking that it's 3 days old at this point and I should just return it.
The other isolation test (in addition to trying a different card) would be to try that Lexar card with a different camera. But that's probably academic at this point. Bottom line: if it doesn't work... it doesn't work. And if you can solve the problem by getting a different card... save yourself the headache.
I've purchased several cards because it's clear that the size options are a function of the card's performance. I'm returning a KomputerBay 128GB card. I'll find out how the Transcend 128GB works when I get it next week. If the Transcend 128GB doesn't work out, I'll be trying Toshiba 64GB and maybe Transcend 64GB (if I feel like pressing my luck). Considering how much we pay for these things, the ability to return it is part of the cost.
Many of the 128GB cards are much slower than their 64gb counter parts. Why not save yourself some money and go with the 64gb Komputerbay card that are PROVEN to work with the RAW at 1080p.
I've only seen 1 or 2 cases of them not working and it was because of a dead card, not speed