For SharePoint Designer, the solution is similar to Dave’s solution.
It seems SharePoint Designer saves local copies of DLLs from your servers, and although everything seems OK, this prevents it from updating the workflow (this is when custom activities are involved, which the question didn’t mention).
To solve this issue:
- Close SharePoint Designer
- Go to
Or, on older versions of windows:
C:\Documents and Settings\%USER%\Local Settings\Application Data\Microsoft\WebSiteCache
- Delete either (choose one, based on how annoyed you are by now):
- All folders.
- The folder that “looks most like your site” (can be more than one:
site(1), etc, and should be the bottom level site, not the root site)
- The relevant DLL in that folder.
- Start SharePoint Designer, save the workflow again, it should be ok.