The same problem and question for me.
The error-message says also that I can uninstall the program and install it again.
Wat is (on a mac) a safe way to uninstall the adobe reader 9.1?
a quick search of the forums would show the probable answer to be this:
Adobe STILL doesn't support case-sensitive file systems on the mac that was introduced around 2003/2004. While no warnings are supplied with the download of Reader, it is common knowledge w/ the CS3 CS4 products that this bug/oversight/issue occurs.
as far as uninstalling, dragging the app to the trash will take care of getting rid of it, but if you wanted all traces gone then you need to also:
1) drag the app to the trash
2) locate preferences file inside Boot Disk/Library/Preferences
3) locate folder inside Boot Disk/Library/Application Support
4) locate preferences file inside Home Folder (your user folder ) /Library/Preferences
5) locate folder inside Home Folder (your user folder ) /Library/Application Support
You may also want to do the same for the "Air" folders which is just a folder in the Application directory labeled "Adobe" inside of which is a file "Acrobat.com.app"... Also, delete outdated Updater folders, or get rid of the updaters completely if you're not keeping flash and shockwave or other adobe products...?
Many thanks for your help.