Hi,
We sincerely apologize for the problem that you have been facing while using a trackpad with Photoshop Elements 11 & 12 on Mac OSX 10.10 (Yosemite).
We have been actively working with Apple to resolve this problem as quickly as possible. We're hopeful this will get completely resolved in an upcoming update of Yosemite(MAC 10.10).
In the meanwhile, you have two options to work around this problem:
1. Option1: Use a mouse instead of the trackpad
2. Option2: Install a plug-in which should workaround the problem
Plug-in installation instructions:
1. Close Photoshop Elements
2. Download this zip file to a location you can easily find (e.g. your desktop)
3. Unzip the file, WhiteWindowWorkaround.plugin, and move it to the Plug-In folder:
• For Elements 12 – //Applications/Adobe Photoshop Elements 12/Support Files/Plug-Ins/
• For Elements 11 - //Applications/Adobe Photoshop Elements 11/Support Files/Plug-Ins/
You can verify the plug-in is installed by launching the Photoshop Elements Editor and choosing Help > System Info... Scroll to the bottom of the text in the dialog and look for the plug-in name "WhiteWindowWorkaround.plugin".
Note: This plugin is a temporary workaround and should be used until this issue is addressed in Mac OSX 10.10 (Yosemite). Please remove this plugin once the issue is officially resolved by Apple.
If you are using a stylus in conjunction with a trackpad, you might see issues with your trackpad. Workaround in this particular case is to use mouse instead of the trackpad.
Hope this helps!
Regards,
vaishali