Netscape interprets frame instructions differently to the other browsers you mention.
It's ironic that while Netscape originated frames, the browsers ability to correctly interpret a frames page or site is a little off the rails sometimes. This is just one of many reasons why most professional web designers avoid frames much of the time in favour of tables.
I'm afraid that without your code nobody can offer a workable solution and frames in general are one of those things that either work as planned or go haywire.
I'd start with a table layout and see how you progress, or run some Google searches about Netscape frames support/problems.
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