Biblio menu item does not expand under drupal5.10

Hi,

I upgraded from drupal5.7 to 5.10 with biblio1.16 and got a compatibility problem:
I have a navigation menu with
…
Biblio

• add biblio
• import biblio

…

The link to the main bilbio page is working, but the expected behaviour (menu expand when the current page is biblio) is not reached any more. Any idea?
By the way, the css style says that biblio is really recognize as active page (different style for the biblio menu item itself).

Thank you in advance for your help in patching this,

Thomas