Robert Hohlfelder writes that Microsoft's Bookshelf software installs a control panel called "QuickShelf" which places an icon in your menu bar. He experienced a problem which is confirmed in article Q171937 (Bookshelf 98: QuickShelf Search From Desktop Takes Long Time) from Microsoft's tech support library. In brief, "there's an incompatibility between the OS 8 Finder and QuickShelf. When you're in the Finder and select an item from the Quickshelf menu, the system freezes for about a minute (the mouse pointer moves, but the system is otherwise frozen) before launching Bookshelf."
When Robert asked Microsoft about this, they replied: "At this time, I don't know of any plans to provide a fix to this problem. The problem, as the article states, and as I've found, only happens with
Mac OS 8.x. With previous versions of Apple's System Software, the feature performs at expected speeds. I suspect that Apple has modified the routine that Bookshelf uses for the function."