[beebleberry]

My friend (who bought my previous iMac) had address book working perfectly and then suddenly the icon to it on her dock changed to the "applications" icon and when she double clicks on it, nothing happens. What might she have done? How to remedy? Do I need to reload the entire OSX 10.4.8 program? Can I just select Address Book?
Thanks!

[chabig]

That sounds like a dock problem. I'd drag that icon off the dock, open the Applications folder, and drag Address Book back onto the dock. It should be simple.

Chris

[kcmac]

If that isn't the problem, download Onyx from Macupdate and clean all the caches, launchd, etc.

[JKT]

Did they move it to somewhere other than /Applications/ by any chance (including into a folder within /Applications) and subsequently apply an OS or secuirty update that modified the Address Book app?

Sounds to me as though that is the likeliest scenario - the updates didn't find the application where it should have been and instead put in a partial install that screwed up the app.