I had been using early versions of Leopard to test Bookdog but not for "actual work". Today, after receiving reports from 2 users of Bookdog trouble with Leopard, I upgraded my Main Mac (an Intel Core Duo Mac Mini) to Leopard and found that my keychain was broken.
A quick Google search showed that Apple has just released a Login & Keychain Update 1.0 for Leopard. However, I suppose because I had not yet gotten the final version of Leopard from Apple, it refused to run on my pre-release Leopard.
So, after being frustrated due to lack of keychain in several apps, I allowed Keychain to reset my keychain. It turns out that what this does is to rename your old keychain, which it cannot open, as login_renamed1.keychain, and create a new, empty keychain named login, which now became the default keychain. So, that didn't help.
What I really wanted to was to fix my old keychain, but clicking Keychain First Aid from the Keychain Access menu didn't work because the old one didn't show up in the list. So, I went to yesterday's backup and copied my old default keychain, ~/Library/Keychains/jk, to its same old location, right-clicked on it, and told the Mac to Open with > Keychain Access. Voila. This now became the active document in Keychain Access, and I was able to he Verify it (problems were found) and then Repair it. From reading the log, five types of problems were found and repaired:Permissions incorrect on ~/Library/Keychains/jk, should be -rw-r--r-- , they are -rw-rw-rw-
Warning: keychain ~/Library/Keychains/jk is missing the .keychain extension
Keychain search list not properly configured
Item “pop.sheepsystems.com” has unspecified value for port attribute
Item “smtpauth.earthlink.net” is a duplicate; this item's port attribute is not set
Finally, I was able to File > Make Keychain jk Default and I was back in business.
My conclusion is that some "security fixes" made Leopard fussier about your keychains than Tiger was, and that Apple forgot to include an update script for people whose keychains have had a long and sordid history like mine, which was born probably in 2002 or 2003 under Jaguar on my old 667 MHz Powerbook G4.
Your situation will be different than mine because you'll be installing the final version of Leopard. If you have trouble, I would recommend that you first install the Login & Keychain Update 1.0 for Leopard. and, if that doesn't fix it, try the Keychain First Aid from the Keychain Access menu on your old keychain like I did. Read this article on keychain problems and this article on where to find Keychains for more info.
The latter article refers to a "login" keychain. I believe that this is incorrect; they mean the "default keychain". Do not confuse the "default keychain" with the keychain named login. Usually they are the same, but apparently they don't have to be. My "default keychain", is still named jk.