Seems a lot of people have this problem, and someone wrote a script to fix it.
See here: http://www.polycount.com/forum/showthread.php?p=1251347#post1251347
Also, note you need to copy the script in the Photoshop/Presets/Scripts folder for it to show in the Scripts menu. Once it's there, you can assign any keyboard shortcut to it - CTRL+Z of course
Photoschop CS3 and up i think.
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