Run the repair CD, it's a stand-alone boot so doesn't matter what OC
has been installed / gone awry etc. You need to verify that the HD is
OK before you go any further.

I tried booting
with a copy of "Active Boot Disc" I found in "my box of tricks" and I was
able to boot up Kubuntu.I then googled boot- repair for ubuntu and I have
installed this via the Terminal..can anyone tell me how I run this in KDE?

Can you boot to a previous kernel from the grub menu or does grub not work
at all?

No it didn't boot at all,just a black screen and GRUB Error.Checked out the
Hard Drive for errors and it tested OK.I then used one of the MBR tools
included and I now have Kubuntu back!

Good that you got it fixed and if you needed to run MBR tools then the
root cause was evidently a corrupted partition table. Only thing to
watch for now is if it happens again.

If the BIOS has been set to boot the CD/DVD first, then the Samsung should boot
and fix it. If it doesn't the Hiren's Boot CD has the Samsung hard disk tool,
plus others.

Personally I'd try the Mint KDE to see if it could fix it in some way. Would be
nice if the Puppy 64-bit Live CD could fix it, but I haven't tried it yet.