I am not involved in the encoding part. I did not write one single code for encoding. I get 3rd party XML files and i just want to decode them. To be very clear on this: I can't change the encoding, it is not my software, i do not develop it and i never had. I just got the source code for the de and encrypt part, so i may be able to import the XML files. I never wrote a single line VB code in my life. To be honest, i don't believe security is the issue, the developer just don't want anyone to be able to open it. That may not be an excuse for bad code but so far, i can't change it, i'm just happy now to be able to decode.
OK, I rebuilt Qt 5.5.0 after removing the environment variables, but it unfortunately did not solve the problems I described.
I was ultimately able to get the VS addin 1.2.4 working in VS 2013 by specifying the Qt installation as being at C:\Qt\5.5.0\qtbase instead of just C:\Qt\5.5.0. I was able to create a simple Qt GUI program and run both Debug and Release builds.
But the remaining problem is that all Qt tools like designer, assistant, and linguist all crash as soon as they are started. In each case the event log holds an entry like this,