I am of the opinion that Mavericks simply cannot be updgraded from Lion 10.7.5. I have tried everything related to this issue in every post I could find - to no avail. Really poor form from Apple. Are they seeing the frustration in these posts from their loyal customers and just choosing to ignore them? They must have a short memory. This is why Microsoft was deemed uncool and why everyone left them for Apple. Now that Apple is top of the pops, it seems they're doing the same thing.
To Apple - would it not be a good service to your many customers who are really battling with this issue to simply issue a patch to fix this? Think of what may happen if you continue to ignore us; we can't upgrade to Mavericks, all our software eventually becomes unstable and unusable and we are forced to choose another operating system. By then I'm sure Google or some other major player will be keen to takeover your disgruntled customers and offer a nice usable, friendly replacement to Apple Macs. So enjoy your market leading position while you can Apple. Your days at the top may be numbered now.
Of course, if there's some simple fix available from anyone who upgraded from Lion 10.7.5 to Mavericks has managed to achieve - please do post it here for us all to read. But if it doesn't come from Apple, then the above rant sticks.