Following this thread, I was having the same issue. Clock would run for a month and then the display would freeze. Tried several SD cards and even tried Micro SD cards with adapters.
I did many flashes, restores, formatting and copying the image again and again. Not an issue of making the image, but every time it would to the freeze after a couple of weeks or months.
jfesler was the genius that helped me solve this. It's not the capacity, its the speed!
I was using SDHC, XC 1, and HC 1 cards. I was told to use 80MB/s - class 10 - UHS-I version at least.
I took a chance and bought Refurbished 16 GB cards off Ebay and the clock has been perfect: ebay.com link: SanDisk SD ULTRA SDHC 16GB 80MB s LOT 10x
Just my two cents...