I made a discovery the other day regarding this issue. Like many of you, our shop uses a few “suites” of software products, which includes Autodesk suites. I think this particular error I was experiencing originally, is specific to Dynamo, but I might be wrong. While I’m not 100% sure which way this happens, (I believe it varies depending on the way in which you deploy/install the product), it seems that if you install a suite that includes Revit/Dynamo, it will install IronPython 2.7.3.
Some disucssion here:
I noticed this because I just installed Revit 2018. Some time after that, I opened Rhino 6 WIP and saw the error again. The solution was the same as noted earlier, to uninstall ironpython 2.7.3 from the windows control panel->Programs and Features.
I am certainly not requesting any assistance for a non McNeel product, just wanted to note that this was our experience. I will also note that this solution does break ironpython components in dynamo.