Open up task manager (Ctrl Alt Delete) and then the processes tab. You can see how much RAM and CPU usage is being used by Farmscapes. I found it to be around 266 000 Kb which is ten times higer than other arcade games that I checked, though the graphics for that particular game were much better than the games I checked. Keep an eye on the memory usage and see if it rises as you continue to play. If it does it may mean there's a memory leak, which is usually due to poor programming. You can see CPU usage by clicking on the network tab. See what the performance is prior to starting the game then again while it is running; (without closing Task Manager)., you can then see the difference when you play the game.
I've never had a problem playing the game, but then I have 16GB of RAM on this particular computer, so rarely get problems related to lack of memory and my cpu has four 3.4GHz cores so again usually no problems.
Norton is notorious for giving warning. I'd ignore the warnings and continue to play the game.