Unfortunately, from time to time, I have to use SharePoint Designer. However after renaming my account I started getting this error:

Server error: The version of Microsoft SharePoint Foundation running on the server is more recent than the version of SharePoint Designer that you are using. You need a more recent version of SharePoint Designer

While this error can be caused by the actual error message, in my case it was completely bogus.

Issue

SPD was trying to login with a cached credential. The account wasn't valid any more.

Attempted resolutions

Clearing the 2 SharePoint Designer cache locations didn't work.
Un-installing and re-installing SPD didn't work.

Fix

The credential was cached in windows credential manager. However if you look there, you probably won't notice the trees for the forest. In my case I just cleared the lot using a handy batch file from https://gist.github.com/tomfanning/77f20a1bb50055e915f4.

The downside of running that is that it will remove all your cached credentials.