The problem is reproducible when Enable Field Editing on Lists is unmarked on the preferred inventory part form being used. As a resolution, user can modify the form as follows:
1. Navigate to Setup > Customization > Entry Forms. C
2. Click Edit link beside the preferred form.
3, Mark the Enable Field Editing on Lists check box.
4. Hit Save.
When user runs the item list view and chose Inventory Item type, you are now able to use Inline Edit functionality.