Where are "Problem Types" used?

[CJ]

G'day folks,

Under the Configuration | Maintenance submenu, there exists a choice (Problems...) to maintain problem types.

Where are problem types used?  I can't find any dialog that provides the list of available problem types.

Thanks in advance, much appreciated.

[thomaskilian]

I guess they should appear under "Project Information/Project, Metrics...; Risks Tab " and there under the Type drop down. This list is empty now.