Error: Can't launch ModelSim-Altera Simulation software

I know that this is a somewhat old thread ... but I would like to put my two cents as others may benefit from my solution. I did removed the .altera_quartus hidden directory, and I still had issues with it. However, I went a bit further and then deleted the .modelsim file ... and that did it. Issue went away. Please note that these are hidden files and thus the "."(dot) is in front of the name.