Can't browse some older backups via Time Machine interface
Problem started after updating to Yosemite. I am running 10.10.1. I can find all my backups, going back to 2010 in fact, when browsing my external FW800 hard drive directly in the Finder. But if I click the menubar icon and choose "Enter Time Machine," I can see some recent backups for some folders, but I cannot access some older backups that I know are there on that same drive. The window title bars in the TM interface are totally grayed out for those older backups. But again, there are all on the same FW800 external HD, and I can search them just fine and extract the files just fine using the Finder.
Is the Time Machine interface totally broken in Yosemite?
Clearly there is nothing wrong with my external FW800 HD, otherwise I wouldn't be able to manually browse and extract files via the Finder. And yes, it makes regular TM backups every day too. It's only the "Enter Time Machine" UI that is partly broken. I say "partly" because some backups (very recent) display, but I cannot access all the backups. It's very strange.
Any thoughts would be appreciated.
Thank you.
iMac, OS X Yosemite (10.10), March 2009 DuoCore, 8GB RAM, 1TB HD