Sigma and small compact flash

I have a Sigma SD9 and 10, just picked up the 10 to replace a 9 with a bad shutter. Took the 10 out for a test spin along with a Verbatim 2GB compact flash. Of course I did not bother to test the 10 with the Verbatim as I had tested it with a 1 GB card when it arrived. To my surprise the early Sigmas will not work with a Verbatim Card, My SD 15 will work with the Verbatim card, but the 9 and 10 will only work a Transcend 2GB card. Clueless as to why. My early Sony's use Compact flash and work with CF up to 32GB without issues. I found couple of Transcend 2 GB cards on line, not many at that size, don't know how much longer they will be made.