sounds weird, I know, but having had all sorts of weird experiences with SD cards and Micro SD cards sanDisk cards included, just wondered, how are you connecting it to your PC?
The reason I ask is that on a fairly new machine running Win7.1 I have found that if i insert the microSD into a USB adaptor it cannot read it or at best can only format to 32gig, but if the card is put into the holder that came with it my machine can see it and format it to its full size
Phone(s) Note II SlimKat, SII NeatROM, Nokia N8-00
Tablets: Transformer Prime Hairy Bean 2.31, Transformer Infinity Cromi-X, MeMo Pad HD7, Acer Iconia A100 (retired)
(but one of the 2 transformers has got to be sold