1603 is a catchall error which MSI returns when it doesn't quite know what went wrong. Quite often, this error is returned when a custom action within the installer failed. To determine the actual cause, MSI logging will usually help. MSI can log to various levels, and finding the source of 1603 errors sometimes requires the highest level. Use the /l parameter to have MSI create a log file. Here's an example:

msiexec /l*v c:\msi.log /i setup.msi

This will create a fairly large log file, which you can scan through looking for the error.

A common reason for the 1603 error is that an installation file was needed (more precisely "was expected") and couldn't be located by the installer. When deploying from Admin Arsenal this can happen if the application you are installing has multiple installation files (usually one or two EXE's with a bunch of .CAB, .DLL or other file types) AND you didn't check the "Include entire directory" checkbox on the Deploy Software window. Remember that Admin Arsenal will deploy the file that you select as the Deployment File however if there are other files that are needed in the installation these files need to be included in the deployment. Checking this box will take care of that requirement.