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" Must be at most 5000 characters "
I'm blocking google from about 600 pages to avoid dup content filter. (tried meta tag block, but yahoo responds to "googlebot" meta tag also)
(<META NAME="GOOGLEBOT" CONTENT="NOINDEX, NOFOLLOW">)
Is this just an error that google site maps is posting. Or can your robots.txt be too long?
If there are more then 5000 characters in that box (which only shows what is contained in your robots.txt, all edits are not saved to your robots.txt file) you will also get the error.
Hope that helps, your not alone on that message.