Runtime error 75 is caused by the user not having permission to modify the .ini file in the RezStream folder. To fix this issue use the following steps:
1. Log into the computer as an administrator.
2. Navigate to C:\Program Files or C:\Program Files (x86) if it exists on the system. (where C is your local had drive.
3. Right click on the RezStream folder inside Program Files (or Program Files (x86)) and choose Properties.
4. Go to the Security tab.
5. If you are using Windows Vista or later click the Edit button.
6. You can then choose Users from the top selection of accounts.
7. Select the Full Control check-box.
Once you have completed these steps the application should have permission to update files in the RezStream folder.