if you right click on your program icon and select properties / compatibility tab, you should see an option towards the bottom to tick 'run this program as an administrator' - if you do this it should run automatically that way without you having to do it yourself; it might be worth doing this with version 17 as well, just in case the programs are interferring with each other...

no consolation, but you are not the only person having issues with 17 to 18 upgrade [I'm assuming you did this under the update service and did not buy version 18 seperately]