This is for Moodle 1.5.x which I tried the most recent codes but it didn't get fixed. I know that the function of print_question_formulation_and_controls() was totally rewritten in 1.7.x...

Change #1.
Reason: In original state moodle leaves input fields in a quiz enabled, this confuses instructors as sometime the input might be changed by accident while reviewing. Purpose of this bug fix is to disable the input during review.

File(s) effected: /mod/quiz/questiontypes/multichouice/questiontype.php
Function/Part of file effected: function - print_question_formulation_and_controls (around line #248)

Change :
Replaced
$readonly = $options->readonly ? ' readonly="readonly"' : '';
with
$readonly = $options->readonly ? ' Disabled readonly="readonly"' : '';

- Readonly does not work for most of the input types used in HTML tagging, disabled should be used to make the input type completely diabled.

Change #2

$state->raw_grade = round($state->raw_grade, $quiz->decimalpoints);
// Add line to round answer to the number of decimal points
// the instructor input in the interface
// This fixes the problem where people scoring 9.99999999999E-06
// gets truncated to 9.99999999 because the sumgrades is stored as
// VARCHAR(10)

Hope this could be some help for people who are still running 1.5.x out there...

Peace...