We're developing on Apple's OS X Leopard 10.5.8, and we've found a another bug that causes files to disappear irreversably... It's easy to reproduce. Try this:
1. Copy a folder from a shared network folder
2. Create new files in the folder
3. In Finder, undo the latest action (which was to copy the folder)
The files you just saved are gone and can't be restored or found anywhere. Please prove us wrong. Not good anyway!