I had the same problem with the beta version of windows 7. This is the solution I found.
To refresh and reset the icons cache, go to the following folder:
C:\Users\\AppData\Local\
To see the hidden AppData folder, go to Organize -> Folder and Search Options -> View tab, and select Show hidden files, folders and drives, and uncheck Hide protected operating system files (Recommended).
Once inside the folder, delete IconCache.db. Create a new file named IconCache.db, and set it to Read Only attribute in Properties (if the file is not read only, the cache won’t be reset). Then restart the computer. Remove the Read Only attribute of IconCache.db file, and the icons cache will be refreshed. The step will restore the desktop shortcut icons to their lawfully icons.