Updating fails under "Program Files" directory without running installer as administrator

Updating application packages normally with online installer fails on extracting if the application has been installed under "Program Files" directory on Windows. Running the installer as an administrator solves the problem, though. Furthermore, installing the application into another location, e.g. "C:\My App" directory, does not cause the problem on updating.

When checking the installer log on verbose mode (see the attachment), it looks that renaming of files (e.g. "MyApp.exe" -> "MyApp.exe.tmpUpdate") fails, most likely due to permission issues.

Installation of the application succeed in the first place, but updating the installation fails like this on the first file from the first package being extracted.

I encountered the problem with official QtIFW 1.5.0 release, but reproduced the problem also with 1.6 snapshot 2014-06-19_66 and when building QtIFW from master branch (latest commit 08d9cf5c07be959bae88e5bcc7737b6ef9faa144 on 2014-07-30).