I recently appealed to the forum for a cure to the above problem when all of my thumbnails disappeared and hung Bridge. The cure is as follows and may work for some of the other thumbnail ills stated here. Courtesy of Adobe Support
Purge the central cache manually.
1. Open Bridge CS3.
2. Choose Bridge CS3 > Preferences > Cache (Mac OS) or Edit >
Preferences > Cache (Windows).
3. Note the folder path that is listed beneath Cache Location.
4. Close Bridge CS3.
5. In the Finder (Mac OS) or Windows Explorer (Windows), navigate to the
folder path that you noted in Step 3. Then delete the folder named data.
On Windows XP, the default cache location is \Documents and
Settings\[user name]\Application Data\Adobe\Bridge CS3\Cache.
Note: On Windows, the default paths include hidden folders. To make
hidden folders visible:
1. In Windows Explorer, choose Tools > Folder Options (Windows XP) or
Organize > Folder And Search Options (Windows Vista).
2. In the Folder Options dialog box, choose the View tab.
3. In Advanced Settings, select Show Hidden Files and Folders.
4. Click OK.
Purge the central cache manually.
1. Open Bridge CS3.
2. Choose Bridge CS3 > Preferences > Cache (Mac OS) or Edit >
Preferences > Cache (Windows).
3. Note the folder path that is listed beneath Cache Location.
4. Close Bridge CS3.
5. In the Finder (Mac OS) or Windows Explorer (Windows), navigate to the
folder path that you noted in Step 3. Then delete the folder named data.
On Windows XP, the default cache location is \Documents and
Settings\[user name]\Application Data\Adobe\Bridge CS3\Cache.
Note: On Windows, the default paths include hidden folders. To make
hidden folders visible:
1. In Windows Explorer, choose Tools > Folder Options (Windows XP) or
Organize > Folder And Search Options (Windows Vista).
2. In the Folder Options dialog box, choose the View tab.
3. In Advanced Settings, select Show Hidden Files and Folders.
4. Click OK.