With regard to things that one might put in .htaccess
The Total choice hosting forums recommend
php_value max_execution_time 300
(does anyone know what it is by default and whether Moodle is changing that default?) to lengthen the time that a server allows php scripts to execute for, and
http://httpd.apache.org/docs-2.0/mod/core.html#timeout
timeout 600
or something to increase the amount of time before the apache server times out. Again, does anyone know whether Moodle is changing that default?) .
One also might consider adding
ErrorDocument 503 /reallysorry.html
and a reallysorry.html file (in the same folder??) so that one could at least apologize to those students that have lost their test scores.
As one student pointed out, if one is using random questions, then not only does the student get zero on the quiz, the next atttempt may also have different questions so they will have to start again from scratch.
This would not be a problem if I were using Moodle in a more socially-constructive way, in line with its design methodology, of course.
Tim