Since the idea is to "buy low, sell high", it seems like the time to buy. So many of my co-workers put all their 401k money in the high-risk funds during the tech bubble, and over the last year, long after things were tanking, moved it into something else. I guess they think you should buy high and sell low. All they do is whine about how badly they are doing.
I have my 401k divided (not equally) among a low-risk index fund, a growth fund, a small-cap fund, and an international fund. Then I move some of the money around yearly to keep the proportions the same. That forces me to buy funds when they are down and sell them when they are high. This approach is known as "asset allocation" in case anyone wants to research it.
I probably won't have 20%/year growth, but slow and steady wins the race. 10% per year until I retire will bring me a very happy ending.