Viewing RAW file thumbnails in Adobe Bridge

Question

Hello folks have a problem which is driving me crazy and I'm hoping someone might be able to give me some pointers. Until recently I was able to view my NEF RAW files as thumbnails in Bridge, click on them and they open in camera raw fine. But all of a sudden though, as I open a folder in bridge I get a brief display of thumbnails which then all convert to just a white sheet icon. If i click on any of these identical icons then the file opens as normal in camera raw,but I cant see the thumbnail preview to know which shot is which. Has anyone had/solved this problem - any ideas as to what it might be causing it? All ideas gratefully received. I am using Elements 8 and Bridge CS4. I have looked through Adobes threads and they had some trouble shooting tips on the issue but these have not worked.
One of the issues they mentioned was checking if your bridge files were in the right place. I am not sure if the bridge file should be inside the Elements file or or not - i am wondering if this might be the problem as i accidentally moved my bridge file and then moved it back to the applications file - so i have included a screen grab of where my files are. and this is what the NEF - RAW thumb looks like instead of a thumbnail
Any help or pointers very GRATEFULLY received

Answer 1

Since no one else, like Barbara has replied more to this, at least publically, I will give some suggestions although I'm a Windows user and it would seem you're on a Mac.
The momentary flashes of image followed by a white sheet icon means that Bridge is initially showing you the camera-embedded JPG preview image, which typically has black bars, and then what is supposed to happen is Bridge uses its ACR to render each RAW using Adobe settings and recreate a new preview.  Apparently something is wrong with Bridge's usage of ACR so the Adobe-specific preview never gets created. 
Your "new" D300 has been supported since CS3 ACR 4.3.1 so it isn't your CS4 ACR version being older than your camera that is the problem, unless the model of camera was mis-reported. 
A clarification question: is it the case that NEFs from both your older camera and the newer D300 fail, now, in Bridge?  Another question would be what version of ACR is being used in Bridge and what is being used in Elements.  You can figure this out by doing Help / Plug-ins... / Camera RAW in Elements and maybe there is something similar in the Bridge preferences area.
As far as what could be wrong:  on a Mac, I believe there is one ACR plug-in for Bridge and another ACR plug-in for Elements, but I have no way to verify where to look on the Mac for them.  Your symptoms suggest that the PSE ACR is ok, and the Bridge ACR went missing or was damaged, recently, and you may be able to fix things by updating the Bridge CS4 ACR plug-in on the Mac to whatever it thinks it needs, or ACR 5.7 if you want the newest one compatible with both CS4 and PSE8, although PSE8 can be updated to ACR 6.1 which wouldn't be compatible with Bridge CS4.
First, try to use Bridge / Help / Updates to check for a new version of ACR and install one if it finds one to install.  If it sees nothing to update, then try to manually install it via the instructions on the Mac-ACR 5.7 updates page.  There is an install for CS4 and an install for PSE 8.  It isn't clear if you can merely use the update for PSE 8 or need to also do the update for CS4.  I would try both updates if you can find folders that match both the PSE and CS4 ones mentioned in the instructions. 
To find the ACR 5.7 update for your Mac:
Go to http://www.adobe.com/downloads/updates/
Change the drop-down up top to Camera RAW - Macintosh and Go
Click on the ACR 5.7 link.
On the page that comes up there is a download and instructions for various products including PSE 8.
You may need to clear your previews cache, again, after installing.