There is a known anomaly with CloseView versions prior to 7.0 (that is, those
versions before System 7) and the Macintosh Display Cards
4*8, 8*24, and 8*24 GC in the NuBus Macintosh. Your symptoms are typical of
this anomaly. The only workaround for using CloseView with these cards is to
upgrade to System 7.
CloseView behaves gracefully under System 6 in other Apple-supplied video
environments: Macintosh Classic, Macintosh IIsi built-in video, Macintosh IIci
built-in video, Macintosh LC built-in video, Macintosh Plus, Macintosh SE,
Macintosh SE/30, Two-Page Display Card, Portrait Display Card, and Macintosh II
Video Card. We have no data regarding third-party video cards.
The version of CloseView that ships with System 7 is compatible with the 8*24
style of video cards. Users wishing this functionality are encouraged to
upgrade to System 7.
Note that though in very brief testing we didn't encounter any problems using
CloseView version 7.0 on Macintoshes running System 6.0.x having an 8*24 video
card, Apple did not formally test this configuration nor is this a recommended
configuration.
An alternative is to use third party CloseView-like programs, such as Stepping
Out from Berkeley Systems, Inc. For more information, search under Berkeley
Systems.