I have a solution which include severeral installshield LE Projects. In the error list in Visual Studio I get the error 6221: Could not resolve primary output but I got no reference to which Project was faulty. I resolved the problem by deleting all primary outputs from all setups and readded them again.
IMHO I should Always be given information about which Project the problem pertains to.
This is a known issue for solutions in which the project for the output to be resolved is not in the directory containing the solution or a subdirectory of it.
For example, it will happen if your solution is at C:\docs\solutiondir and your vcproj file is at C:\docs\someotherdir, the problem will happen. It won't happen if you move the vcproj file to C:\docs\solutiondir or C:\docs\solutiondir\subdir.
For example:
ISDEV : error -6221: Could not resolve Visual Studio .NET project output "Projectname.Primary Output" from component projectname.Primary Output
In the above error message, it is clearly shown that project name will give you in which project primary output has the issue.
