I had the same problem, but on my Wife's MBA running Mountain Lion. I use the quick look feature all the time on my own MBP and noticed is was missing. The solution, as with all things Apple is really quite simple.
This is assuming that you are describing the same thing as I am, so if not please ignore...
The 'eye' icon was missing from the tool bar, which meant I could not 'preview' files before opening them (btw - didn't know it worked with music files as well!).
All you need to do is;
go to View menu
select Customise Toolbar option
You then get a window. All you do is drag the icon that you want into the Finder toolbar you have open (i.e. drag it out of the small menu window you have just opened) and drop it onto the small outlined space in the open tool bar
No need for re-installs!
Guys Ive done 8 hour research on this stupid thing. Its actually a bug comes with itunes 11. Follow below links instructions and degrade itunes to 10.7. Everything is comes backup. We have to wait until apple sort it out..
Hope this would help..
hey. do not know if anybody mentioned it before but as i read the todays posts when i was sitting and playing wirth my mac i had an idea what it might cause (but its maybe to simple to be solution).
when your in the finder (where some of the con´cerned are located) hit command + j. There is an option to preview icons. if it is disabled you dont see a play icon nore the cover-art. if have set this as standard the hole system is/all files are effected by this.
as i sad, maybe to simple to be the solution to the problem.
mhh, okay - as i thought -> to simple ;-). have you tried to reset the quicklook framework as i mentioned earlier in the thread? it seems as nobody has tried this this yet... i got no answers for that.
the terminal command is: " qlmanage -r "
also you can take a look here:
@djlashes: Unfortunately this did not solve the problem.
Does anybody try this following (part of) solution?
(But it's only for people who know how to handle iTunes libraries!!!)
Open a new user account.
Make a new iTunes library called 'itunes', nothing else!
Import some files with embedded album art.
Drag such a file back to desktop and you should see the icon of album art. Everything is like it should be.
Now copy this itunes library to your first user account.
(but first rename your old iTunes library different from 'itunes' e.g. 'itunesorigin')
Open iTunes and point it to the imported library called 'itunes'
Drag one file of itunes to desktop, now miraculosly all audiofiles in all of your itunes libraries should show up album art IN FINDER and preview and quicklook. In my case it's so! All seems fixed.
Unfortunately this is not stable. As soon as I open my old library 'itunesorigin' the problem starts up again. All files who were opened in a finder window or dragged to desktop do not show the icon of album art. I can fix this by openimg the new library 'itunes' but again it will not be stable.
Does anybody know more with this information?