What is going on with this? How can i possibly trust this thing with any amount of BTC when it just replaces my wallet.dat ??
Any explanation for this?
The wallet.dat file holds your private keys. If those private keys have bitcoins associated with them and you load the client with access to that wallet.dat, it will show those bitcoins. If you load a fresh wallet.dat or one with no bitcoins associated with the private keys, it will show that you control zero bitcoins.
The block chain may have to be fully synced to see your most recent transactions.
It's pretty straightforward.
If you have a computer that is problematic (hardware or software issues), any number of things could be going wrong.
If you are just swapping wallet.dat files willy nilly without knowing what you are doing, you may run into issues.
Also, I wouldn't store private keys on any computer which is connected to a network.
How did my Wallet address just change? I did nothing to make it change. I just opened my wallet nothing more.