I was upgrading IPAM for a client today - from version 4.3.2 to 4.5
I had a lot of issues with a stuck Config wizard and webconfig/database errors....
Found the answer though: If the earlier version is installed with a domain-admin account and the new version is installed using a local admin-account, then the installation fails.
Resolution: Uninstall the old version in add/remove programs first and then install the new version. Just doing an upgrade is not possible.
did you run into this again in any other upgrade past this one?