"Stuff" dissapearing from Spotlight search

Question

What is causing this to happen?
What can I do to fix it?

Background

I use Spotlight to launch my applications much like Quicksilver and have recently found that many of my applications aren't showing up in the Spotlight search.

Context

I am on a MacBook Pro running Mac OS 10.6 and have been using Spotlight without any problems for almost a year now. I switched to 10.6 when it was released almost a month ago and this problem didn't start until about 2 days ago and was not right after an update to the OS.

I know someone is going to say it so I will just get it out of the way right now. "Use Quicksilver" I am currently using Quicksilver until I get Spotlight working again. I don't like the idea of things disappearing from Spotlight so I would still like to figure out what's going on and fix it.

Answer

Credit to joshhunt and choge for their answers. Both their answers completely answer the question but joshhunts question got selected because that is what I needed to fix the problem. I have written a how to on my blog with the combination of their answers.

Solution 1:

First, make sure Applications (and the others that you want) is selected in System Preferences > Spotlight.

If that does not work, it is possible somehow indexing got disabled. In terminal, run the following command:

sudo mdutil -E /

Still, if that fails try deleting the Spotlight index and start indexing it again:

sudo rm -r /.Spotlight-V<TAB>
sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist
sudo mdutil -E /

On my machine, the Spotlight index was .Spotlight-V100, but I have seen it as other, that is why used tab completion

Solution 2:

In System Preferences > Spotlight there are two settings that may have been changed to cause something like this:

The "Applications" category may be set not to display in results
Your Privacy list may be set to exclude certain directories that contain applications.

It is also possible that the Spotlight index is not updating if the applications that are not showing up are new ones.