Problem
Every time I try to add a product Item to a Service Quotations, it fails with error 500.
Answer
This happens if all pricing levels are deleted from the System Setup.
1. Navigate to the affected list in Admin > My Company > Lists > Inventory > Products Pricing Levels.
2. Add a Product Pricing Levels Item.
3. Add a Product Item to a Service Quotation.
Note: The save should complete successfully and you will no longer see error 500.