Hallo,
ich würde einmal versuchen die Installationsdateien auf den PC zu Kopieren und die Installation nicht mit setup zu starten, sondern mit cwblaunch.
Wichtig ist auch, dass wenn gleich das aktuelle Servicepack dabei ist, dass die Microsoft Fixes auf dem PC installiert sind.

IBM i Access for Windows ? Service packs

Required action before installing 7.1 service packs available after April 2, 2012 or 6.1 service packs available after June 2009

All IBM i Access for Windows service packs available after April 2, 2012 require that you install Microsoft security update(s) prior to installing the Access service pack. The update(s) specifically address security concerns involving Microsoft Visual C++ 2005 Service Pack 1. While we do not believe there is an existing security exposure to any current or previous client service packs, IBM is following Microsoft's recommendation and will, therefore, require this security update to be applied before installing the client service packs.

Download and install the correct vcredist_XXXX.exe file for your system.
NOTE: If you have a 64 bit system, in addition to installing the correct vcredist_XXXX.exe file for your 64 bit system, you will also need to install vcredist_x86.exe (32 bit version) since IBM i Access for Windows will run both 32 and 64 bit executables on a 64 bit PC.

The Microsoft security update can be found at the following location:
(Note: There is a drop down box labeled "Change language." Select the appropriate language for your installation.)
Download Microsoft Visual C++ 2005 Service Pack 1 Redistributable Package MFC Security Update from Official Microsoft Download Center (link resides outside of ibm.com)

You may install this update any time prior to installing the next service pack for IBM i Access for Windows. The update is compatible with existing versions of IBM i Access for Windows. Please make plans to have this update applied before installing the next service pack.

For a visual representation of this process, click here (00:09:08).

After you have installed this Microsoft security update, you may proceed to install the next service pack for IBM i Access for Windows at your convenience.

For more information about the security exposure, see:
Microsoft Security Bulletin MS11-025 - Important : Vulnerability in Microsoft Foundation Class (MFC) Library Could Allow Remote Code Execution (2500212) (link resides outside of ibm.com)