Will a higher class SD card reduce the risk of crashing my Galaxy Ace? I was using my class 4 32GB SD card in my Samsung Galaxy Ace quite happily until I filled it up to a certain point (which point, exactly I'm afraid I can't find out and don't know). Once the SD card reached a certain percentage of its capacity (Somewhere in the >20GB used area) it started going into the "Sleep of death" bug, where it cannot be woken up after going into lock.

I then deleted some non-essential stuff, and the phone worked with the card quite happily for about 20 minutes, when the card died. I haven't been able to revive the card on my PC or phone.

My theory is that the processor in the Ace couldn't handle that much data on such a low-speed card, which would explain the sleep of death, but not the card failure. Is there any merit in this idea? Would a better class 32GB card have a chance of avoiding the sleep of death, or am I indulging in some wishful thinking?

Apparently the problem is very widespread in Galaxy Aces (according to the manager of a phoneshop I brought it in to), and it seems to happen the Nexus One aswell.

Any thoughts would be much appreciated.
Its because of you are using Max amount SDCard that an Ace can support. 
Ace supports 32Gb Maximum, and you are using the same. But Its fact that Ace supports 32Gb ,but it may cause problems mounting that much higher amount. 

You can try 16GB class 10, it may be accurate.