Large multi layered Tiff, PSD and PSB files which have alpha channels, masks and layers, etc. do not show appropriate previews in Bridge (nor Windows for that matter). Many of these are very large 2-4GB, but even a typical 30-60MB file with certain alpha channels and masks are also problematic with previews. I believe the problem appears mostly when the base images ar 16bit since the 8bit version exhibit properly most of the time.
Is this an issue which has a remedy?
Photoshop CS5, Windows 7, 64bit.
Check your thumbnail option in Bridge prefs...you'll need to up the "Do Not Process Files Larger Than" settings...note, it'll take a while to rasterize those big previews so grab a cup of java while Bridge does the crunching...
As Jeff said, this should fix the very large files, but I would recommend to post in the Bridge forum, or on http://feedback.photoshop.com if you still have trouble with 30 -60 Mb files.