Update to Mac OS X v10.5.2 or later to resolve this issue.
This issue is caused by using 'synthesized' fonts on Mac OS X v10.5 or v10.5.1.
The fonts to avoid are:
- Helvetica Oblique
- Helvetica Bold Oblique
- Courier Oblique
- Courier Bold Oblique
Note: It may not be possible to reopen the domain file after iWeb unexpectedly closes.