I had a similar issue (except I was coming from 4.9.5 ddr 1.99.n) it seemed to be that the dates on a later release file were older than those on the one that I already had installed.  Trying to install from codeplex failed too for the same reasons.

So I set up a test environment and in there I changed my host pages to use minimal extropy and made sure that my web.config had dnnmenu as the default provider.  Having tested that the host pages worked, I uninstalled ddrmenu (including files) and related web.config statements and then installed the correct version of 2.00.1.

All was ok after that, I'm still testing the 6.02 release with my set up but that's the route I'll take when I do put it live.