You need to check the cursor you're starting from. I think it has multiple rows for the same records. I had the same thing hapening ones, this problem usually occurs when you do a join with another table. I think you're using a join to get your v_tmpart table. The problem is not in this select but in the select before this one. This is a possibility by the way not a certainty.

Hoping to help you with this.
Juri