Looks like Eclipse is doing some things under the hood, part of which is opening port 49251. Don't ask me why. My recommendation: don't run the unit tests in Eclipse. Make the developers run the unit tests from the command line (you said the tests ran fine from Hudson, so make the run the same script on their desktop).
I'll add this to the long list of ways that Eclipse can make your life miserable! Personally, I only use Eclipse as a glorified text editor. I rarely use any of the supplied wizards. And I never build or run tests from within Eclipse - all that I do from the command line.