Check the existing thread for cards that work and don't work in the C6 -- the C5 is the same as far as compatibility goes -- seems that the really fast cards don't work for the most part.
adata 2gb 150x sd card works fine in My VPC-C40 & My C5, I dont understand why people r having these problems, maybe they are formatting them on their PCs before trying to use them in their cams?
I took my AData 150x 2gig card straight out of the packaging & put it straight into My C40 & it works perfectly, it also works in My C5, I think if they are SD Cards & the cam has the SD logo the card will work, just like any vhs tape will work in any vhs recorder