Ahh, sorry. The file attempts.php does *not* exist any more. The statement before was from memory, but things keep changing in moodle...
In my version of the quiz module (latest CVS) there is no reference to the file attempts.php anywhere. Therefore I guess that the problem is with your installation.
I guess you were talking about the "View x quiz attempts" link in the "Info" tab when you're viewing a quiz? If that is the case, make sure that the file view.php in the quiz folder is the correct version. If that doesn't solve your problem try copying over the complete quiz folder from the downloaded package (replacing all existing files) again.
Hope that helps,