use different library in different Mac machine.
the library in Macbook Air is mostly freshly created.
i experience this problem since somewhere in Aperture version 3.x and Mac OSX 10.7.x
currently, Mac mini and Macbook Air are running Aperture version 3.3.2 adn Mac OSX 10.8.
JPEG, TIFF and CR2(canon RAW format) would have the same problem randomly.
Are all images from the same camera?
How much RAM do your machines have, and full are your disks? I sometimes see corrupted previews displayed, if the projects are huge or the images larger than 1 GB.
not from the same camera.
multiple cameras with different models. mostly are Canon. TIFF file for external editing. JPEG files from point & shoot DC and iPhone etc.
Mac mini has 16GB RAM with 300GB+ diskspace
Macbook Air has 4GB RAM with 100GB+ diskspace
most of my RAW file size around 8 - 30Mb.. just TIFF files can reach to 900Mb, but only a few..
Of course the corrupted image is not a preview but a version, big difference.
When this happens if you hit the M key to bring up the original what happens?
I'd almost say it was a problem with the video card but you say this is happening on multiple machines so that's not likely. There could be some strange bug in the video drivers, I've never experienced this problem and I don't have either a mini or an air so it's difficult to say.
You may need to contact Apple on this, given your description of multiple machines, multiple libraries and multiple cameras there doesn;t seem to be any common thread to go with.
One last thing you might try, when the problem occurs have a look at the console logs to see if anything is concerning video is being logged. That would at least give Apple something to go with.
Can it be that you are using any plug-ins, the same plug-in on all machines? For example the Nik-plug-in HDR Efex Pro 2? then compare the images posted in this post to your random corrupted versions: