For several blackberry models, if the battery drops below a certain threshold it cannot be charged from a PC. This solution mentioned above should work since it uses a wall adapter.
There is also another cable solution on Amazon that I got which actually has a mode to charge even a dead battery. There are several versions available depending on the variuety of devices that you own. I got one as a corporate gift (apple version) and bought the other one (non-apple version). Here is the link Amazon.com: csquid
hope you get it (ahem) up again.