The 2000 version of that software is known to not work very well on Windows 2000. Go
here and read the blurb; the "More Info" links under Windows 2000 in the chart at the bottom are all dead. I went to Windows 2000 when it first came out, Symantec had it splashed all over their page early in w2k's release that the "2000" versions of their software were not compatible with w2k. So I gave my NAV 2000 to my sister and bought 2001 when it was released and it ran flawlessly. I know it sucks, but that's how it is.
Your problem sounds incredibly annoying. Pester them enough maybe they'll upgrade you to 2001 for free. They changed their support contractor a year or two ago, and my downloaded version on my wife's Win98 machine couldn't be recovered with their recover utility because the support provider of course had different servers. I called and whined and got free upgrade to 2001 for my trouble. I avoid such debacles now by purchasing the CD.
HTH