The old version 1.5.4 was removed using the installer first so I guess that rules out a conflict with an older version.
When I compare the bin folders of 1.6.0 and 1.5.4 the biggest difference is the VS-2008 runtimes that 1.6.0 uses and 1.5.4 doesn’t use. I guess to properly install it, administrator rights are needed, however the installer doesn’t seem to complain about this and the machine I had strong security rules in place.
I also noticed a difference in the manifest file, but I guess that has to do with proper installation of the VC-2008 runtimes.
I’ll try it this weekend on another machine using admin rights.