check the utilization of the switch during the time of issue
first thing switch will drop is the likes of telnet traffic and allow critical traffic through if the switch gets maxed out or is under pressure
check how many running telnet sessions there are on the switch and if they have been left to hang , you could also console in run debug telnet and then try telnet in from another pc and see what then switch returns
by the way you should not use telnet and move forward to use ssh its unsecure even inside your lan someone could see your passwords if they sniff the wire
