Analytics Conversion Tool exception with WFFM

I have just upgraded a project in Sitecore 7.2 IR to Sitecore 7.5 IR. I have also WFFM module, which I am trying for some time to upgrade from version: 2.4 rev. 141008 into version: 2.5 rev. 141014. The first step would be to run the conversion tool. I did the data optimization on Analytics database with success, but I cannot get through the next step: running the Analytics Conversion Tool.

It suddenly stops working, throwing the exception: Could not load file or assembly 'file:///C:...\Sitecore.Analytics.ConversionTool.DMSWorker.dll' or one of its dependencies. Operation is not supported. (Exception from HRESULT: 0x80131515)

The dll is present in the folder. Any help is appreciated!

I know this is from an era ago, but after spending a whole day with the same issue, I thought I'd share the resolution, just in case someone else comes across this. It turns out, it was just a matter of the dependent DLL files needing to be "unblocked".

To quickly unblock all of the DLLs in the folder, open up a PowerShell window and run:

gci c:\ToolPath | Unblock-File