Here is how to replicate the bug:
1) Add new catalog price rule “5% on all products”.
2) Open any existing product, and save it. After saving it will have “5% on all products” in the list of specific prices
3) After that try to duplicate this product. You will get the following error:
Duplicate entry '10-0-0-0-0000-00-00 00:00:00-0000-00-00 00:00:00-1-0-0-0-0-1-3' for key 'id_product_2’
Tested on PS 1.6.11 and 1.6.16. Most probably this happens in all 1.6.x versions