sharding_system_namespaces.js relies on the wiredTiger storage engine being compiled into the server. This assumption does not hold on 32-bit platforms. Specifically, the test's call to the "create" command fails with the following:

{
	"ok" : 0,
	"errmsg" : "wiredTiger is not a registered storage engine for this server",
	"code" : 72
}