Does it boot to an operational state? Can you telnet to it?
What speeds did you try? Newer hardware may use a 115200 console speed.
Possible speeds in newer hardware:
0 = 9600, 1 = 4800, 2 = 1200, 3 = 2400
4 = 19200, 5 = 38400, 6 = 57600, 7 = 115200
See http://www.cisco.com/en/US/products/hw/routers/ps259/products_tech_note09186a008009433b.shtml
If none of those speeds work, make sure that you have hardware flowcontrol off on your terminal emulator and also that the console works on other Cisco devices (to make sure wiring is OK).
If all of that fails, you may have a hardware issue.
