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Have you tried to install the XOOPS files via shell? This tends to be the most reliable means of installing them.
Again, grasping at straws, but it's possible that the distro you downloaded could have been corrupt on the mirror or that the FTP software you are using may have altered a file. Try installing a fresh version via shell from a different mirror. and see if you can reproduce the error.
I agree that this is a serious issue, hence all possible avenues must be explored.
Also, what version of Linux? I run a bleeding edge distro of MEPIS (Debian based), and it's been known to "touch" files on occasion.