As I begin deploying new apps at my client site,  we made a discovery that we were easily able to correct.

After installing a .NET 2.0 app that uses Crystal Reports, we were unable to run Crystal Reports from our .NET 1.1 applications. We got an error indicating that it could not find the CrystalReports.Engine assembly.

The short story is that reinstalling CR .NET 1.1 after CR.NET 2.0 fixes the problem.

For the more curious, I did a little more exploration. I uninstalled the CR for .NET 2.0 but whatever it had stomped on did not fix itself and the 1.1 reports still did not work.

Then I reinstalled 1.1 which worked again and then 2.0 on top of it which again broke 1.1. (Just verifying that this was the direct cause.)

Lastly, we installed CR.NET 1.1 after CR.NET 2.0 and then all of the reporting works fine.