What is the OS of the machine you are using? Is it the same or different on the machine you are installing on?
What dependencies do you have in your package? Are there dependencies on other packages you have installed on your machine but may not exist on the receiving machines? Have you run the install process with logging to see where the failure(s) occur?
As VB6 reached end of life in 2008, you may also be running into a situation where other machines might have updates that cause this issue. I’m thinking, in particular, of potential issues in XP SP3, the MSI Installer, or the IE version on the machine that may be causing this. My bet(s) would be on the MSI Installer updates.