I've created a batch script which can be run as administrator. There I have the most successfull installations:
install.bat:
pushd %~dp0
Msiexec.exe /I "Adobe Photoshop CS6 x64.msi"
Just save this batch file in the folder where the generated msi package is, rightclick the batch and click "run as administrator". The "pushd %~dp0" line takes care that the script goes back to the directory where the batch and msi file is, the default for an elevated command promt is "C:\windows\system32", but there it wont find the installer there.
I would appreciate any response to this from Adobe!