Problem: I'm starting to have birthdates that default to 2029 when I input 1929, as an example. I get an error that says "The Birthdate is in the future, please adjust".   And when I try to do the global age update I get errors.

Solution: Date issues like this are normally caused by changes in your Regional Settings under Control Panel.

Go to your Control Panel> Regional and Languages (or Regional Settings in XP).

On the Formats tab choose Customize this format button.

Choose the Date tab.

Make sure your Short Date is M/d/yyyy.  Also check the Calendar to see its options for "When a two-digit year is entered, interpret it as a year between:"

See this screen print from Windows Vista (XP might be slightly different):