Hendrik
I am strictly an Elements Windows user.
I suspect that the Fusion Drive is at the core of your Premiere Elements 12 on iMac Fusion issue.
But, I have seen many reports of slow performance of Elements products when iMac Fusion drive was involved. Please clarify what you have stored on the fusion drive? Are that Premiere Elements source media stored on it? Where are the Scratch Disks directed?
From what I have read, the Fusion drive consists of two drives, one traditional hard drive about 1 TB and SSD about 128 GB. Is there any way to take the Fusion drive out of the equation and just use one traditional hard drive. From the following article, it sounds like the traditional part of the Fusion drive has the specification of only 5400 rpm.
Apple Mac Mini with Fusion Drive review - CNET
http://forums.macrumors.com/showthread.php?t=1524676
Please review, consider, clarify and then we can decide what next.
Thank you.
ATR