Logitech's drivers have been implicated in failures to install Leopard, and certainly as a result of reading about those issues, I have no intention of installing them again on my Leopard systems. (I did a clean install, so the blue screen problem didn't actually hit me.)
However, I can't type on the standard (latest) Apple desktop keyboards, and much prefer my Unicomp buckling-springs one. But Apple's keyboard layouts don't actually match PC keyboards very well. So although I do *have* a Logitech mouse, I was only installing the drivers in order to get at the Logitech keyboard layouts.
You see, the Logitech keyboard and mouse drivers are only necessary to drive the special function keys that festoon Logitech equipment; but just to get the normal typing keys mapped correctly, you only need the basic layouts. It turns out you can just install those keyboard layouts, and quite easily.
If you're comfortable in Terminal, this single command will do everything you need to do in one shot (assuming you've downloaded the drivers):
unzip -j ~/Downloads/lcc231.zip '*LCCKCHR.rsrc' -d '~/Library/Keyboard Layouts'
For the command-line averse, keep reading for a much longer way of doing it through the Finder -- but one that doesn't require Terminal at all. By the way, this hint will work just fine on earlier versions of Mac OS X; it's just that on Leopard it's necessary to avoid installing the Logitech software; at least until Logitech updates their driver software for 10.5.
Here's the non-Terminal solution:
Mac OS X Hints
http://hints.macworld.com/article.php?story=20071102162602375