On some computers, I can't change public-folder permissions from Outlook 2002, but I can from Exchange System Manager (ESM). Why is that?

ESM and Outlook 2002 use two different, and incompatible, versions of the Messaging API (MAPI) DLL. Exchange 2000 Server puts its version of the MAPI DLL (6.0.4417.0 for Service Pack 2—SP2) in \winnt\system32, but Outlook 2000 and later expect to find the MAPI files in \program files\commonfiles\system\mapi\1033\nt. Outlook installs a small stub MAPI DLL in \winnt\system32; the stub routes all MAPI requests to the Outlook MAPI implementation. The stub generally doesn't bother Outlook, but it does make public-folder administration a headache because Outlook and ESM each expect to see only their own MAPI DLL. To fix the problem, make sure that you have the correct versions of the libraries in the correct locations.