This has been a problem for a very long time. Some of my blogs, especially the primary install, will have pages go into a permanent redirect loop errors for no apparent reason. The solution? Go to the permalink settings, use "custom" but enter the same permalink, click and save and then all works just fine.
I can't seem to find any cause for it to happen periodically but it just does and only with WordPress. My primary blog on the root has the least number of plugins so it's definitely not those. This problem occurs on the root blog more than other blogs. The home page is fine - it's just the internal pages that get caught up in this issue.
I've seen others have this problem with no solutions. Hoping there is an answer or something that needs to be cleaned out in the database.