This isn't a "government conspiracy" sending out bogus transactions. It's some jerk.
If you need to sell Bitcoins right now, Coinbase and Kraken are still up and running. Bitstamp is off line, and Mt. Gox is, as usual, screwed up. Mt. Gox hasn't paid out US dollars since June 2013. Whether they are incompetent, broke, or crooked is a subject of considerable speculation.
There's a technical fix in the works, but it will have the annoying side effect that when you spend Bitcoins in your own wallet, some Bitcoins you are not spending will be tied up for an hour or so. Bitcoin wallets don't really have an "account balance". What they have is a collection of items of different values. When you spend Bitcoins, the wallet software tries to put together a set of items that's over the value to be spent, with one output to the recipient and one output ("change") sent back to you.
Until now, you could can spend that "change" immediately, even though the distributed network hadn't yet confirmed it. It looks like that will be disallowed, and only confirmed items will be usable. The way this looks to the user with a wallet program is that you have a "Balance" and an "Unconfirmed" amount. Soon, when you spend, the "Unconfirmed" amount (which you can't spend) will go up for a while, then go to zero when the network catches up. Bitcoin is a distributed "consistent eventually" system. "Eventually" is about an hour. Longer during busy periods. (That's the next Bitcoin problem. The whole network has a limit of about 7 transactions per second. A few times in 2013, that limit was hit.)
Expect everyone except Mt. Gox to have this straightened out in a few days.