1. what is the address holding the 20BTC?
2. is it transaction of satoshidicke sending back a prize?
3. is the wallet damaged?

if it is a transaction sent but never confirmed i is possible to create raw transaction using same inputs. Think about it as double spend. Also the pywallet is still supported by JackJack.

hate the break it to you: the 20 BTC in your wallet is undependable. the transactions have not confirmed since 2012 and are not in any client's transaction list. unless they're in a block, you can't spend them.

If there are unspent funds for any addresses, you can transfer those keys to a new wallet, rescan, and the funds will show and can be spent.   You don't need pywallet for doing this, standard bitcoind has everything you need.

Step 1.) Make sure you have a good backup of your existing wallet.

Step 2.) Extract keys from existing wallet.
 - http://bitcoin.stackexchange.com/a/3532/153  (first set of instructions)

Step 3.) Close the client, move existing wallet out of the way, and relaunch which creates a new, empt wallet.

Step 4.) Import keys
 - http://bitcoin.stackexchange.com/a/3532/153  (second set of instructions)

I don't remember if you need to start the client with -rescan after.  It doesn't hurt if you do.

SatoshiDICE never got the transactions because they were never accepted by the network.  There is nothing SatoshiDICE can or should do as the Bitcoin transactions for your wagers never confirmed.

Now why this is happening?

What appears to be happening is that your client has some double spend transactions.

That can happen a few ways accidentally (e.g., you have two copies of your wallet.dat and are making spend transactions from both) or purposely (you have a script that tries to wager with SatoshiDICE and then also attempt to double spend the bets that lose via race attack, Finney attack, etc.   There are even situations where if you were specifically targeted, you could see funds on one confirmation but then when you spend them they are invalid -- but that is pretty easily preventable.  Here are the various methods:

 - https://en.bitcoin.it/wiki/Double-spending#Attack_vectors

So, the end result is you have wagers that never got processed and never will.

Unfortunately, the Bitcoin.org client doesn't deal well with these -- there is no way to manually remove the transactions using bitcoind.

The easiest thing to do would be to send your remaining funds to a new address in a new wallet and start clean.

A way to fix the wallet you have involves perofrming wallet surgery to remove the offending private keys (using pywallet) and then rescan.

Well, it's 1.9% less normal than to lose 100 BTC. You should probably stop now.

If not: Be sure to post when you lose. It's not good to have gamblers speak only when they're on a winning streak.

And how much have you spent?

Martingale strategy is the process of burying yourself into one big pile of shit.

Thats the most direct way of understand what you did on satoshidice.