There is a serious ownership/ permissions/ entitlements fault in my 10.7 install.
1) After swapping the stock drive for an Intel SSD of the same size in my Mac Mini 1,2 (2006 -ish?), I performed a clean install of 10.7 via target disk mode; That is, I put the mini into TDM and mounted it via FW400 to my iMac which I booted using a 10.7 install USB drive.
2) The install went smooth and the machine boots by itself as expected all the way to the desktop.
3) I try to install the 10.7.5 combo update via Software Update, it fails due to bad checksum.
4) Knowing I get corrupt downloads from several CDNs (incl. Apple) through my janky cable internet, I download the standalone 10.7.5 package to a USB stick at the local library and, having brought it home, etc, run it from the mini's desktop. Fails for unknown reason.
5) Console log indicates that before the installer even started to unpack the updates:
14-03-25 4:18:59.771 PM authorizationhost: SFBuiltinEntitled: Installer.app >is not entitled for system.install.apple-software
14-03-25 4:18:59.813 PM authorizationhost: SFBuiltinEntitled: Installer.app >is not entitled for system.install.app-store-software
14-03-25 4:18:59.853 PM authorizationhost: SFBuiltinEntitled: Installer.app >is not entitled for system.install.app-store-software
14-03-25 4:18:59.856 PM com.apple.SecurityServer: Failed to authorize right >'system.install.app-store-software' by client >'/System/Library/PrivateFrameworks/PackageKit.framework/Versions/A/Resources/>installd'  for authorization created by >'/System/Library/CoreServices/Installer.app' 
What I've tried: I've tried installing less significant things (like the iTunes update) and get the same error.
I've tried every permutation of repairing disk permissions and fsck from active partition, disk in target mode, single user mode, safe boot, etc. No effect.
I've tried chown-ing things, still no luck.
Somehow the installer has become sandboxed and cannot do stuff, for lack of better language. I'd love some help with this!