Most Bonds are issued with a specific "coupon" or interest rate, have a maturity date and are tradeable. Bond traders bid the
price of the bond up or down based on a number of factors including the perceived credit worthiness of the issuer.
Auction Rate Bonds are issued with a specific maturity date, but the interest rate they pay is set at regular auctions. They have an advantage to an issuer in a declining interest rate environment because the issuer stands to save lots of money if the auction results in lower interest rates.
The problems arose when the confidence in the auctions collapsed. Some were held weekly, others bi-weekly and others monthly.
If you had purchased some of these into your account from your broker, you expected that they would be easily sold at the auction, should you want the cash. When the auctions began failing, investors got (understandably) pissed because they now have a security for which there is no market, or one that has narrowed considerably. They were represented as an alternative to Money Market funds. Not quite as liquid but nearly so. I had read about them and learned a bit about them back in November and put up a thread about them in the Personal Finance and Investing Forum. Here is that
thread. By February, it had become apparent there was a major problem with the auctions and I posted a reply to my own thread, stating there were no longer something one should consider.
JP Morgan, Morgan Stanley, UBS & Citigroup have agreed to buy these bonds back from their clients "at face value" which means $1,000 per bond (typically).
That's it. The banks/brokers are taking these bonds back into their own books, and paying their clients face value for them.
It is important to keep in mind that this situation did not mean the bonds were in default at all, it was simply a liquidity problem. The overwhelming majority of these securities continue to pay regular interest payments to the holders and many were "called" by the issuers and replaced in the market with more conventional paper. Even now that the banks have or will buy them back, the issuers will continue to pay the interest rate set at the last auction or call them in.