Windows – java installers and uninstallers return error 1602

I am trying to remove java 6 32 bit and install java 7 64 bit, but after initially having the uninstaller open and execute successfully, asking me to plan a full removal after a reboot, the uninstaller did not come back, and neither does executing it again work.

I've tried using revouninstaller to remove the old java, which seems to be successful, but java 7's installer still won't execute.

When I execute the offline installer, it asks for administrator privileges, loads up the MSI, and then vanishes. After consulting the event viewer I found these entries from MsiInstaller:

Product: Java(TM) 7 Update 2 (64-bit) — Installation operation failed.

and

Windows Installer installed the product. Product Name: Java(TM) 7 Update 2 (64-bit). Product Version: 7.0.20. Product Language: 1033. Manufacturer: Oracle. Installation success or error status: 1602.

All I know is that error 1602 is supposed to mean user cancelled the installation, which leads me to believe either UAC isn't working correctly (seems to work fine though), or there is some registry entry blocking the MSI installer (though I've checked manually).