[SuperBK]

Is this on Linux, Mac, or windows?

It might be that the account you are running Eclispe under doesn't have permission to write to the folders. Try running as administrator or sudo if Linux.

Check to make sure that your eclipse and your jvm that's its running under are up to date. Look at "Help->Installation Details->Configuration tab"

Clean out any previous attempts to install from a file system under
Windows->Preferences->Install/Update->Available Software sites". Look for anything that says "FRC". You could delete the existing site and add it back in again, but that's up to you.

Saw this on Linux: Check the case sensitivity of the link. What you pasted here looks correct, but make sure that's the one you are entering in eclipse is correct.

And finally, a last ditch effort: Try with and without the trailing slash.