Trouble installing Mavericks over Lion on iMac 12,2; hangs.

Question

Hi Folks,
iMac 12,2 16 Gigs RAM, i7  4-core 3.4 GHz 1-TB HD for data, 1-250 Gig SSD for systems - running Snow Leopard on one partition and Lion on the other. (Full hardware description at bottom.)
Purchased new in New Zealand about 14 months ago from Apple authorized reseller; no AppleCare. Not registered with Apple. No seerrious problems since, until this.
Ethernet lan connection to Airport and then ISP's modem/router (Telecom New Zealand, . Fixed IP. No problems there, I think.
Lots of USB stuff plugged in during install, but that shouldn't matter.
Attempt to install Mavericks on Lion partition while booted in Lion partition failed.
Attempt to install Mavericks on Lion partition while booted in Snow Leoepard partition failed.
(Download to Snow seemed to work fine. Installer ran, finished in 20 minutes instead of 35, but when I restarted the computer the startup hung. Shutdown, restart, hangs. Every time.)
Both installations failed with this hang. Restarts done with verbose logging on show the following, repeating ad infinitum (I stopped counting after it got over 5,100 lines -- no I didn't watch 5,000 lines scroll, I went away for a snooze):
invalid sandbox profiile for pid <number> (invalid regex)
Nothing here in the forums, or on the InterWebs about this error or much about a hanging install (which has been identified as one of Mavericks' problems) except to say wait forever (I  think 5,000 lines of verbose logging is forever) or try the install again. I have tried the install again; it hangs at the same point every time.
There is some stuff on the hacker sites about sandbox and this error, but only for earlier OS versions. The fix for them was to replace the sandbox.kext. I'm going to boot into root in Snow Leopard partition so I can do things to the Lion partition, and change that kextfile?! Yeah, Riiiggghhhhttt. NOT.
I suppose I could try the install with all USB stuff disconnected -- but I don't believe that's it.
I suppose the fact that the Lion might not have had the latest software updates to it before I tried to install Mavericks might have something to do with it. I don't believe that's it (certainly is shouldn't be).
Final recourse might have to be wiping the Lion partition (full erase and clean install) (it doesn't have any critical data saved on it; I do all my work in Snow on the other partition, the Lion is for experimenting).
Anyone have any ideas?
TIA and cheers,
M<
  Model Name:          iMac
  Model Identifier:          iMac12,2
  Processor Name:          Intel Core i7
  Processor Speed:          3.4 GHz
  Number of Processors:          1
  Total Number of Cores:          4
  L2 Cache (per Core):          256 KB
  L3 Cache:          8 MB
  Memory:          16 GB
  Boot ROM Version:          IM121.0047.B1F
  SMC Version (system):          1.72f2
  Serial Number (system):          C02FX1DCDHJW
  Hardware UUID:          00528295-A96E-509E-9ED0-3140DEAF77E2

Answer 1

Sorry, bad news for you, depending on your setup.
The answer (provided by an Apple higher-level tech for which I paid -- no Applecare) was that they don't have a clue, but a clean install works.
Yeah, Thaaannnnnnnkkkksss. Knew that.
Clean install (almost) always works (worked) for 25 years.
You don't say if your kit has everything on one partition, or there are more than one.
If you have a big hard disk that's not full, has lots of room, but only one partition, with 10.8 you can dynamically create a new partition without losing data. I don't have the details of the process handy, but it's pretty straightforward.
Then, with the Mavericks installer on the 10.8 partition, and booted to that partition, you can install Mavericks on the other partition (with administrator account). You could use the migration assistant (or whatever) to bring your data over from the 10.8 partition to the Mavericks one. However ...
You might also want, if your hard disk isn't huge, and you don't have two drives of whatever type in the machine, to make the new partition just big enough for the OS and apps, and keep the data on the 10.8 partition.
You can tell the Mavericks instance to use the other partition as your Home directory, instead of the Home directory on the Mavericks drive.
If you have your OS and data on the same partition, and you don't have enough room on your disk(s) for the above procedures, then your best solution would likely be make a Carbon Copy Clone of the drive, wipe it completely, and install Mavericks from some external source other than another partition with another OS, and migrate your data back.
There is stuff on the Web about making a bootable Mavericks install disk on a flash memory stick.
But whichever way you end up doing it, you will have to boot into a clean OS on a different partition or disk from the target Mavericks install partition or disk.
Last caveat: it may be difficult, but not impossible, to maintain your, or multiple users', identity and accounts and where they point, as well as your online IDs.
Hope that helps a bit. Don't give up, but do take precautions (a CCC backup or a Tiime Machine is always wise anyway) and write everything down as you go.
FWIW, I'm not using the Mavericks partition for anything, not even experimentation. I'm still using my Snow Leopard, because it works fine (finally) and is the only way to run Eudora. Until, that is, I solve the problem of running 10.6.8 server in a virtual machine in the Mavericks partition so I can run Eudora under Steve's nose with impunity, and so seamlessly it seems to be running under Mavericks, with full integration (through Parallels).
Cheers from the Antipodes,
M<