Let's take a step back.
Can you ssh into the device. until the answer is yes then all the other stuff wont work.
So forget about everything but that.
You say you are using puttytel to assumedly telnet in.
Why not try normal putty and just attach on port 22 to test the ssh stuff.
Also... Has the networking configuration changed at all during that time at your location?
DHCP Ip address range changed maybe? worth just double double checking your settings... ( I suppose)
One thought: Could it be that you need to empty your ssh known_hosts file?
I utterly forget how puttytel works (It been a while)