Absolutely no one is going to be able to help you without knowing a lot more about your setup. Right now we don't even know what platform you are on (windows or Macintosh), nor the exact versions of ACR and the OS, etc.
Please read this FAQ for advice on how to ask your questions correctly for quicker and better answers:
I'm working on a 3 month old iMac OS X, Snow Leopard, Adobe Design Premium CS5, WD 3TB Hard Drive. Did I cover my bases? And yes, I've CRP is set to "All Images".
And- more info for you all:
Mac OS Extended, Version 10.6.8
Available: 423.73 GB
I'm wondering if it's a simple update that I need to download? I just ran CS5 Updater yesterday.
Thank you in advance.
…Did I cover my bases?…
We still don't know what exact version of Photoshop you are running. It should be 12.0.4.
Nor do we know how much RAM you have installed nor what your memory allowance to Photoshop is.
Save an image as a PSD or TIFF file, to rule out JPEG artifacts.
At this point, I'm leaving this discussion, now that I know you are on Snow Leopard and on an iMac, neither of which I can help with. Sorry.
Am I to understand you expect your thumbnail previews to be sharpened the same as your images? These things are generally at two completely different scales. Sharpening that affects a radius of 1 or 2 pixels in a 3000+ pixel image won't have much visible effect at 800 pixels.
A preview is just that - a preview. You should not expect to gauge the sharpening of the actual image by the sharpness of the preview generated. Image sharpening settings have to do with the development of the image, not the generation of the preview.
I think perhaps you're actually trying to solve a problem where you'd like to see more detailed previews on your monitor, e.g., in Filmstrip mode in Bridge, or for a slideshow. Have you tried investigating the different preview options in Bridge?
Also, something else to look at: In Bridge, choose Edit - Preferences - Advanced... Try checking the following setting, remembering to purge the cache afterward in order to cause the preview regeneration.