unfortunately, the card you bought is most likely a fake. i also was tempted into buying a 16gb micro sdhc from hong kong for about $16. after numerous errors, googling, formatting and re-formatting, i discovered this site:
http://sosfakeflash.wordpress.com/
the ebay seller i bought from--best2all8888--is listed as a known purveyor of fakes. of course i did look at the feedback ratings (not deeply enough, unfortunately), but i've since discovered that the seller bribes people who leave negative feedback to change their ratings, thus ensuring the gravy train continues.
to confirm that your card is a fake, download and run this small app:
http://www.heise.de/software/download/h2testw/50539
it's from a german software site (google h2testw.exe to comfort yourself that this is legitimate software) that writes to and verifies your card. here's what the software reports for my "16gb" card:
Code:
Warning: Only 15001 of 15779 MByte tested.
The media is likely to be defective.
230.0 MByte OK (471128 sectors)
14.4 GByte DATA LOST (30250920 sectors)
Details:0 KByte overwritten (0 sectors)
0 KByte slightly changed (< 8 bit/sector, 0 sectors)
14.4 GByte corrupted (30250920 sectors)
0 KByte aliased memory (0 sectors)
First error at offset: 0x000000000d751000
Expected: 0x000000000d751000
Found: 0x0000000000000000
H2testw version 1.3
Writing speed: 2.31 MByte/s
Reading speed: 3.54 MByte/s
H2testw v1.4
that's right--my "16gb" card really only has 230mb of memory.
if your card is indeed fake, consider filing a report with sosfakeflash, and initiate proceedings with ebay to try to get your money back.
good luck.