This issue used to crop up for my brother until he got tired of Safari nagging him and chose to put a password back on his account. If you have updated to 10.3.9 and have run
Keychain First Aid (found in the Window menu of Keychain Access) but you're still experiencing this issue, you have three options:
1. Either assign passwords to the accounts in question, or,
2. Turn off all Auto Fill in Safari and delete the Auto File entry in the keychain using Keychain Access. That should stop Safari from attempting to decrypt the keychain. As a last resort,
3. Use a third party browser (anything other than IE, of course).
I'll edit this post if I find a better fix. Interestingly, while my brother had this problem, two other accounts that do not have passwords function normally. I believe this is likely due to the fact that my brother's account once had a password, whereas the other accounts were created without any passwords. If I were trying to fix this issue, I would definitely try Keychain First Aid.