After some scouring of the forums here I have seen icon issues related to changing themes, but haven't come across an issue that I have recently.
The other day I took a picture while I was at work and used someone else's computer to transfer the image to their desktop in order to attach it to an e-mail (my own computer here doesn't have the capability of recognizing my BB.)
I guess the Desktop Manager decided to synchronize with the other computer and now my icons for Yahoo! Messenger, Blackberry Help, and Google Talk have all changed to the default (?) globe icon that Browser uses.
I've tried switching between the themes I have as well as pulling the battery, but so far nothing has worked for getting the original icons back.
