I have a group of 7 sites, all have the same problem.
about every 30 hours my sites go blank.
to fix this temporarily I reinstall the three wpinclude/default-xxx files via ftp.
I changed chmode to 644 read only.
but 30 hours approximate, when I look at my sites they are all blank again.
The first time this happened after I installed the JR Favicon for WordPress plug-in. Since then I have uninstalled the plugin.
Does anyone know what I should do to stop my sites from being hijacked?