Hey Martin,
thanks for the feed-back! I had a look at ‘display errors’ as suggested and am totally freaked out :) Not sure I’m qualified for this.
Here is the warning I got:

Notice: Trying to get property of non-object in /home/virtualn/public_html/wp-content/plugins/fv-all-in-one-seo-pack/fv-all-in-one-seo-pack.php on line 2556

If any other (simple) tips, pls let me know.
Thanks again!

Mia