"Object reference not set to an instance of an object." on parametrized reports

For some reason, running reports that are parametrized (prompt for params) returns the following error: "Object reference not set to an instance of an object." Reports without the parameter prompt seems to load just fine. Here is my setup:

Windows Server 2008 R2

Microsoft Visual C++ 2010 x86 Redistributable (v10.0.30319)

MySQL Connector/ODBC 5.3, 32-bit (v5.3.4)

Microsoft .NET Framework 4.5.1 (v 4.5.50938)

SAP Crystal Reports runtime engine for .NET Framework 4 (32-bit) (v13.0.12.1494)

I have tried downgrading the CR runtime to each version down to 13.0.2 with no success. Any ideas how to proceed from here?