I have a client who is trying to install the 1 months trial version of AC 19 on his iMac 2011, 2.7 i5, 32 GB RAM, OS 10.10.4. When he clicks on the downloaded installer a solid black window appears instead of the usual installer interface. He has updated/reinstalled both Adobe Flash and Java 8. Installer works fine on another iMac in his office. Any suggestions?