When you downloaded the map, did it by any chance ask you to replace a file or two? If yes, and if you did, then those files for the two maps could be completely different. One file could have easily messed up the other file (and yes, you can only have one file of the myplants or any other one) and the map. And for your second problem, there could be a file in that other map you downloaded that could have caused a map exporting problem. If that map had any particles of any kind, go to your particle folder and delete any files ending in _0 _1 etc. Hope this helps.