A bug in template?

[cn kene]

A bug in template:

   #set($pager = $site.getWeblogEntriesPager($since, $maxResults))
ok!
                      #set($myweblog = $site.getWeblog("myblog"))
                      #if ($myweblog.name ) weblog: ($myweblog.name ) #end
ok!
but:
                     #set($pager =
$site.getWeblogEntriesPager($myweblog,$since, $maxResults))

  nothing?????????

who can help me?