Save the license.rtf from WordPad. See this webpage (http://wixtoolset.org/documentation/manual/v3/wixui/wixui_customizations.html), specifically this section:
There is a known issue with the rich
text control used to display the text
of the license file that can cause the
text to appear blank until the user
scrolls down in the control. This is
typically caused by complex RTF
content (such as the RTF generated
when saving an RTF file in Microsoft
Word). If you run into this behavior
in your setup UI, one of the following
workarounds will fix it in most cases:Open your RTF file in WordPad and save
it from there in order to remove the
complex RTF content from the file.
After saving it, rebuild your MSI. Use
a dialog set other than the
WixUI_Minimal set. This problem
typically only occurs when the license
agreement screen is the first one
displayed during setup, which only
happens with the WixUI_Minimal dialog
set.