One thing to try is to attempt to access the router via the aux port. If the router is booting ok access through the aux may work and allow you to investigate what is the problem with the console.
I am not clear in the original post whether system information is displayed on the console while the router is booting or not. If the information is not displayed then I would suspect that the baud rate of the console has been changed. The 2500 has 4 possible baud rates (9600, 4800, 2400, 1200) and I would suggest that you try each of the settings and see if it helps you gain access to the console. (It would also be good if each time you change the setting that you stop and restart your terminal emulator.)
If system information is displayed during bootup then output to the console is working and it would appear that there is a problem with input on the console. One possibility is that the console has been disabled (the command no exec on the console will do this). If the aux port works you may be able to check for this. Or you can try an adaptation of the password recovery procedure: reboot the router, hit break during the first 30 seconds, set the config register to 2142, and reboot the router. The router will boot but not read its config file, which may leave the console working and allow you to examine (and correct if necessary) the config file.
HTH
Rick
HTH
Rick
