timer_read() returns negative value in specific condition

There is indeed something wrong with timer_read()
In some occasions both $timers['page']['start'] and $timers['page']['time'] are not set, so $diff becomes very big ($stop * 1000) which gives something like 1162937764105.4 (more then 10 digits)

If $timers['page'] is not set, it indicates that DRUPAL_BOOTSTRAP_LATE_PAGE_CACHE had not been executed (DRUPAL_BOOTSTRAP_LATE_PAGE_CACHE contains timer_start('page');).
Is this normal in certain occasions ?? No idea. This should be investigated. (it would mean that this is a bootsrap.inc issue, and not a statistics.module issue.)

This only seem to happen when enabling 'access log' (so disabling should be a temporary solution).

This is the timer_read function:

<?php
function timer_read($name) {
  global $timers;
  list($usec, $sec) = explode(' ', microtime());
  $stop = (float)$usec + (float)$sec;
  $diff = round(($stop - $timers[$name]['start']) * 1000, 2);

  if (isset($timers[$name]['time'])) {
    $diff += $timers[$name]['time'];
  }
  return $diff;
}
?>

BTW, I think the round(x, 2) should be replaced by round(x, 0) There does not seem to be any use for the extra decimals if we are going to store it in a int field.

An easy fix to this is not to do anything in timer read if said timer is not stared.

Patch is working. Looks like a good solution to me.

Why is this critical??

Committed to HEAD.