I agree, it's most likely down to the SD card.
When I Originally got my KT, I used an old 2GB Micro SD card (NOT SDHC) and I had no problems with it.
Recently I got an 8GB SDHC card and I'd get exactly that problem.
After some searching on this forum I found the following solution will likely fix it (although not everyone has success).
First download SD Formatter:
https://www.sdcard.org/downloads/formatter_3/
Goto the options and select "FULL (Overwrite)" on Format type.
and Format Size adjustment "OFF"
For me, after I did that (and it's important to select "Overwrite"), the problem went away.
If it still continues, try to borrow or use a 2gb NON SDHC MicroSD card and see it the problem stops.