Note: this issue disappeared for the author, after upgrading to Adobe Reader 8.1.
I was being driven around the bend trying to resolve a problem with Acrobat Reader 8 in that it kept crashing within 15 seconds of launching (scroll down to read more).
Eventually, in the Adobe forums, I found that others were having the same problem and it was due to the update plug-in. Most likely some sort of privileges problem, according to another poster in the forum.
The solution given by people in the forum was to choose to remove the Update plug-in by removing it from the application's package. However, I found that there was an extra pane in the Get Info dialog that allows you to add, remove, enable or disable plug-ins. I think it's a more sophisticated way to deal with it.