aakk9999 - 7:43 pm on Sep 28, 2011 (gmt 0)
Google thinks of a canonical in a similar way to a redirect. If you say that one page is canonical of another and then point back with another canonical, it greatly confuses Googlebot. To the point where I've seen people saying that it shows up as a crawl error in webmaster tools.
Yes, this would show as "Redirect loop" in WMT.
Also if you put canonical from A to B and then have 301 from B to A, this also shows as "Redirect loop" in WMT