It's probably your card reader.
Many card readers will not work with Secure Digital cards larger than 1GB (since the original SD 1.0 specifications only allowed for 1GB maximum Secure Digital cards). Even more card readers will not work with Secure Digital Cards larger than 2GB (since the Secure Digital 1.1 specification only allowed for 2GB size).
In order to read larger capacity SDHC cards, you need a card reader that specifically supports SDHC cards (i.e., meets the SD 2.0 or newer specifications).
Chances are, your Sony's card reader is the problem.
You may want to check Sony's web site and see if they've issued some type of update for your reader that allows it to read newer SDHC cards.
If not, your best bet is to buy a USB card reader that supports SDHC (and make sure it specifically supports SDHC). They're relatively inexpensive now (you can usually find them for under $10 if you shop around).
Here are some readers at newegg.com:
Here's one that supports SDHC (the SD 2.0 specification) for $5.99 plus $2.99 shipping:
You can also find inexpensive multi-card type readers supporting SDHC cards. Here's one example for $9.99 with free shipping (and if you scroll through the card readers there, you'll find lots of inexpensive readers).