SSIS 2014 Custom Task Error (when run as 64bit) - Exception deserializing the package "The server threw an exception.

I am developing custom SSIS Task for SSIS 2014 so I just installed SQL Server 2014 and SSDTBI with VisualStudio 2013 so I can design SSIS 2014 Packages.

Everything just working fine except custom Task I developed throwing below exception (only when running as 64bit). Looks like when I set Project to run as 64bit it throws below error. I don't get this error when running under x86 Mode.

The same custom Task I developed works fine in under 2012, 2008, 2005 so I am not sure what's change in SSIS 2014 ????

I have deployed my custom task dll under these folders for x86 and x64 both

• I have changed all of my project references to Version=12.0.0.0 (IN SSIS 2012 it was 11.0.0.0) 
• Registered under GAC (compiled project using .net 4.0 framework).
• Copy dlls under C:\Program Files\Microsoft SQL Server\120\DTS\Tasks
• Copy dlls under C:\Program Files\Microsoft SQL Server\120\DTS\PipelineComponents
• Copy dlls under C:\Program Files\Microsoft SQL Server\120\DTS\Connections
• Copy dlls under C:\Program Files (x86)\Microsoft SQL Server\120\DTS\XXXXXXXXXXXX (Same as above)

Am I missing anything here???

Thanks