Netscape 7 ok?
I don't know. It may depend on whether Netscape 7 uses the same Adobe Acrobat plug-in that IE and Firefox use, but there could be other factors like different Javascript engines.
According to another article, a person claiming to be at Adobe says "This issues ONLY effects the Windows platform. Mac, Linux, etc. users are NOT effected."
The security issue exists in Acrobat 7 only. It was fixed in Acrobat 8, so the best solution is to upgrade Adobe Acrobat.