Right, I have just seen a link below my post which seems to point to me having to modify some files, this is DrByte's reply to known bug fixes regarding php5.2.3 but the title reads known bug with v1.3.9h and old versions of php, but then he goes on to say its only stricktly necessary if using php lower than 5.2.3, which is the bit thats confusing me a bit.
However I have printed off his instructions and having copied my cart as a mirror image onto my hdd, I'm going to have a go later tonight (when finished work) at implementing the changes and see what happens.

paul..