error with "default" bucket. named bucket work OK: CouchbaseLibcouchbaseException Failed to get a value from server: Network error.

php-ext-couchbase version: https://github.com/couchbase/php-ext-couchbase/commit/ff2ed89c6255a2f364640b62d9930732ce597075

duplicates to #PCBC-169, but with php 5.4

I use php-fpm 5.4.13-1.el6.remi.x86_64 ( with nginx-1.3.15-1.el6.ngx.x86_64).
It work OK yesterday. But today: CouchbaseLibcouchbaseException Failed to get a value from server: Network error.

$bk = isset($_GET['bk'])? $_GET['bk'] : 'default';
$cb = new Couchbase("$host:8091", 'user', 'password', $bk);
$a = $cb->get('aaa'); //-> error here

Error with /test.php (& /test.php?bk=default). But OK with /test.php?bk=mybk

After: # service php-fpm restart
Then all (with 'default' & with named bucket) test OK.

I can not reproduce this error now.