Issue with DMT and Vista

[#1]

Could some kind soul please give me some tips on how to resolve this..  I shall be as brief as I can.
Background...
Vista 64 bit on a laptop; trouble free for three years (touch this very large plank of wood!)
Voyager 2110 router.
Been using DMT tool (version 8.07) with no problems for most of that time.
Yesterday afternoon DMT suddenly decided not to run properly, giving a red flashing port 23 window. No connection to the router on DMT but browsing and downloading is fine.
Tried so far...
Deleted and reinstalled DMT, no change.
Marked DMT as an exception in Windows firewall: no change.
Done a port scan: port 23 is not open.
Checked that port 23 is configured as the telnet port; it is.
Telnet service was not installed (I don't think it needs to be for DMT), but installed it anyway and forced it to run. DMT still will not connect.
In DOS command box typed "telnet 192.168.1.1" and got the error message "Could not open connection to host on port 23: connect failed".
Trawled round the web, found lots of people with the same problem but no real answers (including the DMT forum).
Any suggestions would be very gratefully received!

[#2]

A couple of things to try
Disable the windows firewall entirely
Run DMT as an administrator (right click  and select run as administrator)

[#3]

Thanks Jim...  unfortunately neither has the desired effect.
I've noticed that even though I delete DMT, reboot and reinstall it, when I run it, the correct login details are already pasted in, implying that they are being recorded somewhere. It would be nice to try a "clean" install of DMT but it's apparently not letting it happen. Anyone know where the login etc details are parked?

PS Jim, is that Old harry Rocks I see before me?

[#4]

It is indeed - as the words say 
I didn't install DMT
I just extracted the zip file into a folder and ran the exe from there
At present I am running it from Windows 7 64 bit but I will reboot the computer and go back to Vista 64 bit to see if there is a problem

[#5]

Hoho...  do you know, I hadn't noticed the words. The scenery is so overwhelming!!  
Found the .ini file by the way, deleted it, but still no go. Yes, when I say "install" it I meant unzip and run. Same as you did.
DMT has been running fine on this laptop for nearly three years until yesterday. Don't think there is a problem with 64 bit.

[#6]

Just booted into Vista 64 bit and no problems.
However I am now running Windows update (164MB worth) and will report back after they are installed

[#7]

I run DMT v8.07 on XP, Vista 32 and 64-bit and W7 64-bit. No problems.
I know that doesn't help solve the problem but hopefully eliminates some generic issues. 

[#8]

Now there's a thing!
Borrowed another laptop, ran DMT and it can't find port 23!!!  Just had a scan through the router settings, nothing has changed, but it must be the router?

[#9]

Np problem here on Vista 64 bit fully patched
Now back on Windows 7 64 bit