Started when i enable memcache module

Hi guys, i have this error warning when i enabled the memcache module.

Warning: array_flip() [function.array-flip]: Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 178 of /drupal7.15/includes/entity.inc).
Warning: array_flip() [function.array-flip]: Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->cacheGet() (line 356 of /drupal77.15/includes/entity.inc).

in one of the $ids array have this value:

$ids = array(
array(
'uid' => 1
)
)

which array within an array is not compatible with array_flip();
a temporary fixed i made below, which i know is not a good idea, please help out.

    $merged_ids = array();
    if(!empty($ids)) {
          foreach ($ids as $key => $value) {
                if(is_array($value)) {
                  $merged_ids = array_merge($merged_ids, $value);
                  unset($ids[$key]);
                }
          }
       $ids = array_merge($ids,$merged_ids);
       $passed_ids = array_flip($ids);
    } else {
       $passed_ids = FALSE;
   }