i think Karan has already some ways to check.
However, you may check out following.
1. You may change your terminal emulation software for accessing the switch. (i.e. instead to putty, you may use hyperterminal or secure crt).
2. As mentioned in the kB, you may set following settings on your emulation software.
a. Baud rate - 9600
b. data bits - 8
c. parity - none
d. stop bits - 1
e. serial break lenght (if applicable) - 100 ms
f. flow control - you might want to check whether RTS/CTS is turned on or off when you are not able to type?
if it is turned on try turning off and vice a verasa.
3. If nothing works out after following above steps, there is mode / factory reset button to reset your switch to factory defult. You may use it and default the switch. better if you have configuration backup.
4. Post reset, you should be able to access the switch.