OK -
From Home/Library delete:
Preferences/com.apple.quicklook.satellite.plist
Preferences/com.apple.quicklookconfig.plist
Preferences/com.apple.QuickLookDaemon.plist
Preferences/com.apple.windowserver.dat
/Preferences/ByHost/com.apple.QuickLookDaemon.5A778CB1-DE16-5C3F-A6B4-EB4726E33F F0.plist
/Preferences/ByHost/com.apple.windowserver.5A778CB1-DE16-5C3F-A6B4-EB4726E33FF0. plist
Reboot.
If that does not do the trick, in my book you are facing two options
1) Move all your data (Files you created) from the bad account to the new and working account.
When you are done and have the new account setup. Eventually delete the old one.
OR - My preferred option
2) Replace the Preferences Folder of the Bad account with the one from the good account.
Back it up first. Then log in to the good account and navigate to the bad account's home/library folder and move or delete the preferences folder.
Then copy from good account the preferences folder to bad account. And reboot. Don't launch ANY apps just yet. Just test the finder. If you start launching apps they will create new preferences etc. So wait until you have copied over the old prefs. you really need.
If it works now, go to the backed up preferences folder and mark the preferences of stuff you know that you need as in iTunes etc. The mark them all with an .i.e red label. Then copy them in to the preferences folder. And reboot. If something does not work after this, at least you know that one of the red-marked preferences file are to blame...