Hmm, si_c.pp is part of the FPC rtl, as such, assuming you installed from your Linux's repo, should be recompiled and ready to use as such. Have you deleted anything or edited anything up there ?
Those files are currently in root space, not your user space. This would only normally happen if you have been running as root, a very bad thing to do. You may need to rebuild the run time library or, probably easier, reinstall FPC.
For the record, if you do want to mess around with FPC files, download the source of fpc323 and build and install in your own space.
Davo
Edit : another possibility is your fpc.cfg file is not pointing to where the .ppu files are, has that been edited ? For a repo install thats /etc/fpc.cfg but a local file in your home directory or working dir will override that.
$> find /usr -name "si_c.pp*" 2>/dev/null
Might be interesting.