Older MacBook Pro (10.7.5) won't update any software

Question

Here's everything that's been stuck in Software Update for a while:
iPhoto Update - 9.4.3
Java for OS X 2013-004 - 1.0
iMovie Update - 9.0.9
Digital Camera RAW Compatability Update - 4.07
Security Update 2013-002 - 1.0
Airport Utility - 6.3
Safari - 6.0.5
iTunes - 11.0.4
If I try to update, all or individually, it'll proceed as normal, sometimes even ask for the restart, but even if it gets to the end of the cycle, a warning message pops up saying none of the items can be installed.
Now, when I say it won't update anything, I mean "anything." I'm running Lion (10.7.5), but Lion disappeared from my list of purchases in the Mac App Store, which I did purchase even though it says I didn't. I've tried rebooting to reinstall it that way because it still shows Lion there, and I even called Tech Support, but they couldn't figure out why it disappeared. I just recently came to the conclusion that nothing updating and Lion not being able to be reinstalled, are likely related.
Anyone have any idea why it won't do any software updates?
P.S. - My model (Titanium) cannot support Mountain Lion.

Answer 1

Ok then, we can rule out the "not enough space" scenario.  Try repairing permissions and restarting your computer afterwards.  If that does not work, set up a new account and try using Software Update.  If that work, we can then rule out system wide problem.