The "insufficient storage available" message strikes us all, and there are many theories. Certain apps seem to be offenders, as they won't install despite GBs of available space, when larger size apps do install. Clearing caches, uninstalling updates, closing apps, and deleting files don't help consistently.
My theory is that it may be related to the Android SDK version used to develop the app, since installation depends on the response to a recommendAppInstallLocation query.
I was trying a similar query with the following commands:
adb shell pm getInstallLocation
adb shell pm setInstallLocation 2
They gave me syntax errors, and suggested the correct commands, which were:
adb shell pm get-Install-Location
adb shell pm set-Install-Location 2
So, I suspect the apps that won't install are written in obsolete script, and would like to see if those of you with cellphones and tablets running other Android OS versions will please attempt to install the app Appinstaller (you can immediately uninstall it after successful installation). If my theory is correct, installation should fail on your N7 running Jelly Bean, no matter how much free memory you have available. It should install with older Android OSes. At some point (ICS?), users should encounter the insufficient storage error.
Let us know what you find out