Yes, you can charge the BlackBerry via USB if the drivers are installed. If BlackBerry Desktop Manager, or BlackBerry Device Manager, can connect to the handheld then the drivers are installed as they should. Make sure your not connecting via a USB hub. Connect directly into the USB ports on the PC/laptop. Try different ports. You should be charging about as fast as with a wall charger connection.
See also: What Is - Device is not charging as quickly as expected with a bus-powered USB hub Support - Handheld does not charge with USB connection to a PC