User's navigation menu disappears or doesn't show up at all

Hi,

(1) I've noticed that sometimes the logged in user's navigation menu will disappear when clicking on home or other pages. Refreshing the page will sometimes show their navigation again.

(2) Sometimes a user and password are accepted, but you need to refresh the page to see your account and user navigation.

anyone have similar problems?

Both problems began once I made the seach feature work,
and when I enabled the cache setting, with a 1 minute minimum cache lifetime.

It still happens when I disable the cache settings.
I'm not too sure if or how the search feature could be causing the problem.

Thanks