The highest form of ignorance is when you reject something you don't know anything about.

Wayne Dyer (b 1940)

Office for mac has determined that your product key is not valid

When launching Excel, Entourage, PowerPoint, Word, you have a message :
"Office for mac has determined that your product key is not valid"

this was probably right after you added the latest update ...

Microsoft strikes again .....or I knew that Office for Mac was a ClusterF*ck
Still...I am sometimes nostalgic too...I keep on looking at it.. so, how to fix your issue:

1) Time Machine*
Go back before the update, restore, et voila ! :-)
(I did a full restore of the /application/Office for Mac)
Save the latest v. of your .doc, .xls, .xlsx , etc files
Tip courtesy of Fran. Thank you Fran ;-)

2 ) Manual
Removing Office 2008 License Files:

If your copy of Office 2008 was installed with an invalid product key, or if you mistakenly used the same product key to install Office 2008 on more than one computer, you must remove the invalid product key and enter a valid product key to use Office 2008.
1. In the Finder, select /Applications/Microsoft Office 2008/Office/OfficePID.plist, and then on the File menu, click Move to Trash.
2. Select /Users/username/Library/Preferences/Microsoft/Office 2008/Microsoft Office 2008 settings.plist, and then on the File menu, click Move to Trash.

-YOU WILL BE PROMPTED to RE-Enter your license, as used before the Uptade

3) Time Machine (simple)

This is an untested Solution
Restore files:
/Applications/Microsoft Office 2008/Office/OfficePID.plist
/Users/username/Library/Preferences/Microsoft/Office 2008/Microsoft Office 2008 settings.plist

leave a comment if you have other solutions

*Time Machine
If Time Machine is not set up on your Mac, this is a reminder: Time Machine WILL save your life.
Time Capsule: Apple just upgraded Time Capsule: for $299 , you have a 1 TeraByte backup disk AND an Airport Etreme base Station <<< good deal


  1. dosent work!!!!!!!!!!

  2. Using time machine saved me from total misery. Thanks for the help.

  3. Joel,
    You are a wise man.
    Time machine is an amazing feature ;-)

  4. Very useful, Time machine saved me again! Thanks!