Unserialized error in bootstrap.inc - one that I haven't run across in searches yet

I've run into one of those unserialize errors, but haven't run into a post about this particular one:

Notice: unserialize() [function.unserialize]: Error at offset 2 of 77 bytes in
\includes\bootstrap.inc on line 478

Apache 2.2.11
PHP 5.2.8

Starting at line 478 of bootstrap.inc:

/**
 * Load the persistent variable table.
 *
 * The variable table is composed of values that have been saved in the table
 * with variable_set() as well as those explicitly specified in the configuration
 * file.
 */
function variable_init($conf = array()) {
  // NOTE: caching the variables improves performance by 20% when serving cached pages.
  if ($cached = cache_get('variables', 'cache')) {
    $variables = $cached->data;
  }
  else {
    $result = db_query('SELECT * FROM {variable}');
    while ($variable = db_fetch_object($result)) {
      $variables[$variable->name] = unserialize($variable->value); <<<< Line 478
    }
    cache_set('variables', $variables);
  }

  foreach ($conf as $name => $value) {
    $variables[$name] = $value;
  }

  return $variables;
} 

Is this a memory issue with PHP perhaps? Thoughts?