Quote from MKTrader:
1) How many weeks ago are you talking about?
2) What would that buy signal have been based on?
I've been in stocks for awhile, but what you said sounds like typical hindsight analysis. "Yeah, you should've invested back in November/December, when stocks were meandering around with no clear direction. We smart guys knew a rally was about to explode..."
A short-term pullback in an uptrend is one of the best times to buy or add positions. However, you certainly need an exit plan. I wouldn't recommend putting your entire 401k into the market now with no plan to take profits or cut losses..