The big buzz in the markets of late is the resurgence of gold prices. Gold just breached a new all-time high, and the incredible run higher in the price of the SPDR Gold Trust (GLD) in 2010 has made gold a shining city on the hill for investors. GLD is up more than 15% so far this year, and the value of the yellow metal continues trading well above both short- and long-term trend lines.

Some have cited the volatility in global currencies such as the yen and the U.S. dollar as the chief reason why gold prices are on the rise. Former Fed Chairman Alan Greenspan agrees with this thesis. He thinks that rising gold prices actually are a sign that investors are getting very, very nervous about the global economy.

Greenspan recently said that gold still represents the “ultimate means of payment” and that if there are serious problems in the currency markets, gold will be the currency to hold. Greenspan also warned that a jump in gold prices could be “the canary in the coal mine to keep an eye on.”

Interestingly, the rise in gold prices also comes amid rising equity values. Take a look at the chart below of the S&P 500 Index. Here we see stocks mounting a rally off of their August lows, and above both short- and long-term moving averages. The rally in stocks and the concomitant rally in gold is not usually the case. Usually we see a sell-off in gold when stocks are rising.

I think the rise in both gold and stocks is something investors need to keep a careful eye on, as it means that we could either be headed for a big correction in gold prices or a big correction in stocks.

If you are long both stocks and gold right now, then it’s time you made sure you have stop-loss orders in place on both positions to protect yourself from a potential downturn in one of these market segments. In my opinion, the recent price action in both gold and stocks is unsustainable. That means a correction could be close and, as such, you’ll want to make sure your money is protected.