Version: 4.6 (using KDE 4.6.4)
I tried this with Konqueror and Gwenview and concluded that it's a common problem.
Simply put: The file requester (file open / save / copy) forgets that I set it to no previews, detailed view mode and so on. The next time it opens, it's with the default settings.
*** This bug has been marked as a duplicate of bug 139475 ***