It seems to be ok now. I’ve disabled both the plugin and the permalinks, reactivated the plugin, and after that reinstated the permalinks. Now it’s OK.
Thanks for the support!
Martijn
I re-installed it, but that didn’t do the trick. The weird thing is that I can embed other tumblr sites, but not my own. Could it be the fact that my tumblr is using a subdomain of my own blog?
Thanks.