Bitcoin wallet/address balance confusion I'm quite new to bitcoins so apologies if i'm being a noob, but I'm very confused!

My bitcoin-qt wallet balance says I have 2.0113406 BTC (which is what I expect).

Now if you check my transaction history:
http://blockchain.info/address/1HvxJibwAAyVqcNY5GVUWvHSwgYybpRGTp

It says that I only have 0.0123506 BTC?

I think the confusion stems from the transaction I made to satoshidice. It says I sent 2 bitcoins to satoshidice but i only actually sent 0.01. Further inspection yields that I actually sent 0.01 to satoshidice and the remainder to address 1EHYT8dFMcDVnkkE9kEoH5T3PBb3bRZdmP. What is that address? Is that one of my addresses that I don't know about?

What's going on?
Your Bitcoin wallet can have more then 1 address. In fact the Satoshi client (Bitcoin-Qt) creates 100 addresses from the start.
Both 1HvxJibwAAyVqcNY5GVUWvHSwgYybpRGTp and 1EHYT8dFMcDVnkkE9kEoH5T3PBb3bRZdmP belong to your wallet and thus the total balance you see it correct.
Now to why this did happen.
Your wallet received 2 BTC. When you sent 0.01 BTC to Satoshidice "input" the previous mentioned 2 BTC where used as "output" and had to be spent in its entirety. Because the output was bigger then the input the Bitcoin client sent the difference to a new address, which also belongs to you.
In our daily life this is known as change money.
You can read about this in detail on the official wiki: https://en.bitcoin.it/wiki/Change