When I use the 'Cover Flow' preview on my mac, normally it shows me thumbnails of my images. Now all of a sudden it's stopped doing that for .ai and .jpeg and just shows an icon etc. tho it's previewing ok with .tif, .pdf and .psd files! I've checked my finder view options and things seem fine...anyone know how I can get this to work again? It's only showing the image thumbnails when I use columns...any ideas?!

I had exactly the same thing last week.
Restarted the machine, and all returned to normal.

similar problem... i run onyx for my op system clean up utility... after it goes thru and does its job it will restart the mac and then it runs faster... i was told about the program which is free.. from reindude durring his visit here after that alls well... basically i can compair it to a windows op systems defrag/disck cleaner... available for os systems. here's the link just pick you version of op system and insatall it http://www.apple.com/downloads/macosx/system_disk_utilities/onyx.html

Many thanks - will give it a whirl

That worked a treat - thanks. Also sorted out the issue of my desk top picture reverting to an older one every time I restarted! YAY!