Please provide more information. When you use the word "terminal" are you referring to a dumb terminal, a PC running ProComm that is connected to the server, or the actual console screen and keyboard on the server itself?
Have you tried changing the baud rate? Try 19200 8 N 1, and 115,200 8 N 1 - those are the two most common now. You could also try 4800 7 E 1, but I doubt it's that - that is for a special application.
If it is just a PC that you are using to administer the server you should be able to reboot it whenever you want - same goes for a dumb terminal. If you are using the actual console screen and keyboard on the server itself then you would have to shut down the server - make sure you know the proper procedure for shutting it down and bringing it back up, and make sure you have a current backup before you ever power anything down - just in case it doesn't come back on!!