Over the last week or so, my much beloved Quicksilver has gotten very, very slow and sluggish. I'd hit the hot key (option-space in my case) and start typing. And then I'd wait. After a few seconds, the command would register and the action would take place.
After snooping around for what the problem is, I found a few web pages that suggested reducing the catalog size. Yes, I did have a large number of items in my catalogue. Therefore, I promptly unchecked many of the items in my catalogue and issued a rescan command. However, contrary to my expectations, this had no noticeable effect.
Apparently deselecting items does not actually remove them. The whole lot is still sitting in memory. They are only cleared out after Quicksilver is shut down and restarted. Ugh. That's the way I had to fix things on my old operating system.
Gripe aside, here's the lesson. To really fix a dawdling Quicksilver, pare down your catalogue and restart the application.