Cisco Catalyst Switch - Not all keystrokes working using console port?

in CCNA & CCENT
Hello,
I have Cisco Catalyst Switch and I when I type it doesnt always produce the character I want, about 80% of the time it doesn't work? I have noticed I get this strange message when I try to login via putty?
I have flow control off, I have tried Putty and Xterm but same issue
▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒CCCCCCCCC+▒#3#3#3#3#3#3#33#3#3#3#3#3#k
^
% Invalid input detected at '^' marker.
Switch(config)#dsd
Has anybody got experience of this issue?
I have Cisco Catalyst Switch and I when I type it doesnt always produce the character I want, about 80% of the time it doesn't work? I have noticed I get this strange message when I try to login via putty?
I have flow control off, I have tried Putty and Xterm but same issue
▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒CCCCCCCCC+▒#3#3#3#3#3#3#33#3#3#3#3#3#k
^
% Invalid input detected at '^' marker.
Switch(config)#dsd
Has anybody got experience of this issue?
Comments
any other ideas?
Sorry, that should read "...with which to test the cable."
They work perfectly fine with many other routers or switches
CCNP R/S