I would just like to thank you all for taking the time to help.
I will use all the information that I now have from you and re-work the cct.

I will let you know of the outcome of my tests.

Kai,

After reading your explaination, would I be right in saying.....

On the 1 to 0 transition, 650uA are sourced by the combination of the weak and very weak internal pull-up resistors, as a result
the potential drop across the 1K pull down is greater than 2V.
And due to the pin being at or greater than the 2V level the weak internal resistor is never deactivated, and hence the continued 650uA source. If however the potential was dropped to less than 2V on the 1 to 0 transition, this pull-up resistor will be de-activated hence, only allowing the IIL current of 50uA to be sourced by the pin.

How would you suggest I do this?
As mention, when a 10K pull down was used the resuly was .......

for a high -> 4.98V
for a low -> 3.55V

for the 1K pull down

for a high -> 1.60V
for a low -> 0.015V

Thank you agian for your time
sun