I either have both 3.6 and 4.0 installed in my lap top at the same time and 3.6 is open and will not let me go to 4.0. I must have doubled my upgrade by installing it more than once. Version 3.6 has been hanging in my desktop and in the doc. Entering Command I it tells me that I have version 3.6. I can see 4.0 in applications but I can not open it because it tells me that 3.6 is open and you can not have 2 open at the same time. This situation will not allow me to trash 3.6. So how do I get to 4.0??