In November 2010 an SEO complained in a Google Webmaster Help thread that when he used the change of address feature in Google Webmaster Tools, it prevented him from doing so because it thought his domain was not a root domain. It gave him the error, "Restricted to root domains only" but it was a root domain.
Google's Susan Moskwa replied the day after and said thanks for the report and suggested they 301 the domain until Google fixes the issue.
The webmaster came back in a few months later and asked for a status update on the issue, in which Susan Moskwa replied a fix will be out in the next release. When that will be, she said she can't say.
Susan Moskwa said:
I'm reasonably confident that we'll be able to fix this in an upcoming release; however, I can't guarantee an exact date for said release (probably within a couple months, ballpark).
The issue was when the webmaster moved from a .co.uk domain to a .com domain. The change of address feature wouldn't work for them. The webmaster explained:
We moved our domain from a .uk.com extension to a .com extension but in webmaster tools when I try to do a "change of address" it says "Restricted to root domains only" even though a .uk.com domain is a root domain.
Thing is, there was a minor release update to Google Webmaster Tools this week for the Analytics link up feature - but I doubt it was a full release.
Forum discussion at Google Webmaster Help.