menu and updatepanel problem

well here i'm facing a.... so just asking for a suggestion....

my project contains a dynamic menu on master page, that is being populated from oracle database (so it's taking little time to load).....and there is also an updatepanel (Ajax control) which contains the contentplaceholder....

while i'm clicking on the menuitems.... different controls are being loaded into the contentplaceholder, and working as expected (partial reloading)..... My menu is a AsyncPostBackTrigger of this updatepanel......

but, while i'm clicking on a menuitems that are directly associated with loading control... the whole page is being refreshed..... reloading the menu takes little time

is there anyway.... so that on clicking the menu item; only the contentplaceholder will be updated with the newly loaded control????