Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Rent-A-Center (Nasdaq: RCII) fell more than 11% on an analyst downgrade, kicked off by weak second-quarter results and lower full-year guidance.

So what: Stifel Nicolaus, a top-rated firm in our Motley Fool CAPS database, cut its rating from "buy" to "hold" after Rent-A-Center missed the Street consensus by $0.09 a share. Revenue came in light by about $2 million, The Associated Press reported.

Now what: Guidance really drove the sell-off. Rent-A-Center, which specializes in leasing household goods, revised its 2011 estimates down slightly. Management now expects $2.85 to $3 a share in earnings, on $2.87 to $2.91 billion in revenue. Previously, executives forecast $2.90 to $3.10 a share. Wall Street had been calling for $2.98 a share and $2.88 billion, respectively. Either way, hoped-for growth has gone missing -- and stock gains with it. Can management reverse the slide? Let us know using the comments box below.

Interested in more info on Rent-A-Center? Add it to your watchlist .