this is happening to me, right after a switch to a new machine and a fresh install of Logic 8 all over again — and of course I updated it to 8.0.2...
yes, the impulse responses were installed in the right place, /Library/Audio/Impulse Responses/Apple/…
the problem is they won't be found in that default location, unless I navigate there from the "open" window
so I looked inside a hundred of the pst files that appear in the library tab when SpaceDesigner is the active plug, for instance
/Library/Application Support/Logic/Plug-In Settings/Space Designer/04 Surround Spaces/04 Surround Outdoor/20.2s Dam Level Two.pst
and found they all referenced the correct location, mentioned above…
so, what am I doing wrong?