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 Acme Packet (Nasdaq: APKT) are jumping with some healthy upside today, rallying by 11% at the high, after Jefferies initiated coverage on the stock with a buy rating.

So what: The rating was accompanied by a $35 price target and some bullish comments. Jefferies believes that, despite recent negative announcements, longer-term drivers of growth in the session border control market remain intact. Jefferies also adds that it believes investors should "take advantage of an attractive entry point," considering shares have been crushed by weak announcements of late.

Now what: I had called the first announcement a case of market overreaction, while the second one just made CEO Andy Ory lose some credibility. With as much pessimism as has been plaguing shares recently, a little bit of bullishness goes a long way, especially as some shorts are likely getting squeezed out of their positions. That said, I still like Acme Packet's long-term prospects as VoIP takes off over the coming years. Acme Packet still has a shot at rallying this year.

Interested in more info on Acme Packet? Add it to your watchlist by clicking here.

Fool contributor Evan Niu holds no position in any company mentioned. Click here to see his holdings and a short bio. Motley Fool newsletter services have recommended buying shares of Acme Packet. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.