** This issue has been resolved in ArcGIS 9.0. **
Rotating a data frame, using Data Frame properties > General tab or Data Frame tools, causes some coverage and CAD annotation to disappear.
This is a known issue for ArcGIS 8.3 or earlier. Only annotation in the orginal non-rotated rectangular extent is displayed.
Converting coverage or CAD annotation to geodatabase annotation is the only workaround to this problem at ArcGIS 8.3.