[fixed by using CMD command processor - see EDIT #4 at bottom]
I had the 134.1445 (13.1 EAP) installed on my Win 7 Home/64 bit machine, and downloaded / ran the 135.406 exe installer (with bundled java). I have not modified the vmoptions file(s) at all.
I selected the "Uninstall old version" option. The installer ran and created the Desktop shortcut. Two issues:
1 - [PROBABLY MY MISTAKE] no uninstallation (the 1445 build is still on the machine, the shortcut to it still on the Desktop)
2 - the new version won't launch - the splash image comes up for a very brief interval, then it just puts up a dialog "Failed to create JVM: error code -1"
I re-ran the installer. It lists the two existing installations of 1445 and 406 - I don't recall having to make that selection on the previous installation,so maybe I missed that checkbox.
BUT that didn't help. I selected to uninstall the existing 406 and delete cache/history but not to delete plugins ... the uninstaller ran... now the 406 installer won't install saying "Please select an empty folder or a folder where IntelliJ IDEA 13.1 is installed as the target for installing IntelliJ IDEA." At this point, after the uninstall the C:\Program Files (x86)\JetBrains\IntelliJ IDEA 135.406\bin directory still exists with three files in it ... idea.exe.vmoptions, idea.properties, and idea64.exe.vmoptions) So I assume my next step is to manually delete the C:\Program Files (x86)\JetBrains\IntelliJ IDEA 135.406 dir and restart the installer.
[EDIT #2 Uninstall/re-installation of 406 did not fix the problem, still get "failed to create JVM" message /EDIT]
[EDIT #3 Uninstall 406 and existing 1445 and reinstall 406 (with manual remove existing dir) did not fix, so now I don't have a working install at all :( /EDIT]
I can still use the 1445 build (so that mistake is welcome!) but how do I move onto the RC?
In case it's useful, my command-line jvm is 1.7.0_51-b13 from Oracle.
[EDIT #4 A couple days ago I installed JPSoftware's TCC as my default command processor... if I launch CMD.EXE nad from that I manually launch idea64.exe then 406 launches fine. Not sure about why 1445 launched OK - maybe it somehow stuck with the previous default comspec? Anyway, I have a workaround, so now the issue is just a comment to JetBrains that the launcher should work with TCC16.