Thanks for the help people!
Strange one this.
I have found the only way to keep the card and system stable was to turn down to X4 AGP in the BIOS. then it runs fine. albeit not as fast as it should
As soon as you turn it up to X8 AGP setting in the BIOS it starts to act up again.
Just to check it wasn`t my mobo I have ran my old ATI 9000
for a series of hours without a hitch!.
I have finally given up. Card is back in its box and off the the shop again. Not sure what to get!. any ideas on what will be a good purchase ?