Actually, nevermind. I figured it out. For a number of the files in the Time Machine backup, you must be root to view them. That actually caused me some trouble, since I didn't remember setting a root password when installing Ubuntu. Here's what I did:

1) Log in with my regular ubuntu account
2) Open a terminal and type "sudo sh" (with no quotes. this will create a shell session with you as the root user).
3) type "passwd" (no quotes)
4) enter a new password for your root account
5) type "exit" to go back to your normal terminal session

Now you should be able to log in as root at the ubuntu login screen (using your new password). You will be able to browse the once-blocked files and directories.

NOTE: If you copy any files from the Time Machine drive that you only have permission to view as root, you better make sure to use the CHMOD command in the terminal (while you're still logged in as root) to change the permissions. Otherwise, you'll do something like copy a file to your desktop, log back in to your regular user name, and then wonder why you're still getting "Permission Denied".

For those who aren't chmod-savvy you can type "chmod a+rw FILENAME" without quotes in the terminal to change FILENAME to read and write access for all.