You need to modify the workflow for the project to make those custom properties active and/or required for each step in the workflow:
- Click on Administration > Incidents > Workflows
- Click on the "Steps" hyperlink for the active workflow(s)
- On the next page, click on the New(Default) step in the left-hand column
- On the Incident workflow step page that appears, make all the appropriate custom properties Enabled = Checked and then click [Update]
This will not be necessary in the 4.0 release because custom properties will default to being visible, and enabled.