Try turning wireless off and then back on. If that doesn't work, try a hard reset.
Typically, it's a carrier issue. Lower-case "edge" means it's searching for EDGE. If the hard reset doesn't work, you'll just have to wait until the carrier fixes whatever issue it's having. I have it happen every now and again, and it's rare that it takes long to fix.
And when in doubt, there's always the search button... ;)
http://www.blackberryforums.com/sear...earchid=904529