Check the properties of both to make sure. Why can't you open two tabs?
yes, I checked the properties for Remeres.
I open 2 tabs, but not to open another tab with another map
map opens above the other
Maybe you've tried to open a map that's been made using the lastest version with the older one or vice-versa
Im sure they have to be the same version.
Every instance has its own clipboard, it wouldn't work.open 2 Remeres not 2 tab