I confirmed this at least on Office Starter 2010. Other versions might be affected. The short story is, there were 3 updates for Office as part of the latest Windows Updates released this week. After installing them, users who are trying to open a Word or Excel file might get prompted to enter a key or purchase Office.
If you are experiencing this, it can be corrected. To correct this, you need to repair Office. Here’s the link with the step by step instructions on how to repair it:
If you need help with the above, contact me.