Environment: Current Capacity Reporter (CCR) 1.5 / Windows 2008 R2 (64 bit)
Problem: After clicking on the 'Test' button during set up of a Data Manager Data Source in CCR, get a HTTP 500.19 Internal Server Error

Solution: Bring up IIS Manager > Application Pools, verify that DefaultAppPool is set to .NET Framework version is set to .NET Framework v2.x. Click ok, recycle IIS and retry the operation.