I cannot reproduce this problem. Here's what I would recommend:
1. Ensure the problem is genuine; go to Entourage -> General Preferences,
and click the "Calendar" tab. Under "Reminders", check "Set default
reminder to occur __ hours before". Then, click OK, and go to File -> New
-> Calendar Event. Does it show __ hours? If not, continue.
2. Download and install the latest Office X updates, which are 10.1.2 and
10.1.4 (10.1.3 is unnecessary). They¹re available from Microsoft.
<
http://www.microsoft.com/mac/downloads.aspx#OfficeX>
3. Check to see if the problem is resolved.
4. If it's not, then rebuild the database. First, go to Entourage -> Turn
Off Office Notifications. Now, quit Entourage, and then restart Entourage
holding down the Option key. When the Rebuild dialog box comes up, choose
to do a Typical Rebuild.
5. If that doesn't help, double-check your preferences to ensure the
checkbox is checked and "hours" is selected, and test again.