Some users have encountered a problem in which, upon either waking from sleep or the screen saver, if a password is required, the computer will prompt for the password twice.
Apple Discussions poster Xdeepsea writes:
"From sleep mode i usually log in my password and then the desktop will display on the screen. For the past 3 months after a archive install of 10.5.2 I have to log-in 2 times."
For some users, this problem started after system reinstallations system updates. Additionally, while it seems to happen most during wakes from sleep or screensaver, some users have had this occur at the login window, which indicates it has something to do with the system's authentication directory as opposed to any problem with the sleep or screensaver functions. It seems one possibility might be the system could be waking up prematurely and then starting the sleep process again, and with each process requiring authentication this could result in two authentication prompts. This may be the case for some users since for them the problem only happens when accidentally waking from sleep with the screen closed such that the computer wakes up and immediately goes back to sleep.
While there are no known fixes for this problem yet, users may try the following to fix the problem. Luckily this problem does not harm the computer, and as such is more a matter of annoyance.
Things to try:
Create a new account Users might try creating a new temporary account in the "Accounts" system preferences to see if the problem is a result of problematic settings in the user's library. Additionally, creating a new account might create properly entered authentication information in the computer's directory, which might clear the problem for other accounts or at least have one account that works properly.
Change the account password If this problem is a result of the account's authentication information not being accessed properly, users might be able to reset this by changing their account passwords to a different one. This can be done in the "Accounts" system preferences, and after the initial change can be reverted back to the original password.
Reset PRAM It is possible this problem could be due to faulty settings in the PRAM that pertain to the sleep functions of the computer. While this might not apply to all situations, a PRAM reset might help in some cases.