Call to undefined function error when opening browser, ok after page refresh

[eluser]webnology[/eluser]
Hi all,

I'm developing my first CI app. Lots of fun, great code and manual. I do have a problem now: If I open my browser, go to the site, I get an error: call to undefined function. If I refresh the page, the site works fine. So the function is really there, but it seems to be hiding the first time. This only happens if I am logged in in the website. I use DX_Auth as a member tool.

All help appreciated,
Kind regards,
Michel