I got the same error as you. I also did Help> Install New Software, then I selected the developer tools, I can click next, but I could not click the Finish button. I have been looking for an answer for this for some time, and everyone is saying the same thing, although this does not seem to work.
Try something else that actually WORKS.
I installed it after 5 minutes:
1 - make sure you still have the original zip file (to me this is "adt-bundle-windows-x86_64-20140321")
2- Copy the contents of the zip where you want it to be
3- This is similar to 1.30 GB (I think), so depending on your computer, this may take several minutes
4 - as soon as it is copied, open it.
5-Go in the eclipse folder, then open the eclipse application (you can even bind it to the taskbar if you use it)
I have had this problem several times and it always works for me.
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