GarageBand: Effects other than Echo and Reverb sometimes cannot be selected
Symptoms
Sometimes the effects in the Track Details area can't be selected, except for Echo and Reverb.
Products Affected
GarageBand '08 (4.x), Mac OS X 10.5
Resolution
This can happen on Mac OS X 10.5 Leopard computers if you grab the Visual EQ by its name and drag it to a different position.

If you grab the Visual EQ by the drag handle (three dots at the left side of the check box), then the issue will not occur.

If the issue does occur, you can resolve it by closing and re-opening the Details panel.
Update to GarageBand 4.1.1 to prevent this from occurring.
This document will be updated as more information becomes available.