Primary link Block disappears ( Zen Theme)

Hello,
first of all thanx for this module it really made my day after discovering that FB blocks my IFrames on Tab.

I had a facebook App showing all the news of my page up and running in about 1 hour ( including changes in the layout).

I have although encountered a problem that seems really odd to me:

Everytime I visit the CanvasPage in Facebook the main menu (Primarylinks Block, Zen Theme) disappears on my homepage. If I go to the Themes-Page in Drupal (/admin/build/themes/select) and re-submit the menu reappears again.

The canvas page is based on a view that pulls all the newscontent, the theme is fbml_fb that comes with the menu.

I have no clue what the reason of this could be, any suggestions?

Thanx

addendum

I have tried with other themes (Garland, artisteer) as well and get the same results. it is though not the block that disappears but it seems that the $primary_links array is empty after the facebook canvas-page has been visited.

It seems the the fbml_fb theme interferes with the Theme registry of Drupal. When the theme List istre-submitted or the theme registry is flushed the menu appears again.

I have now substituted the fbml_fb Theme in my canvas pages for another theme (adapted Zen theme) and it works like a charm.

Again thanx for the great module! Where can I donate?