WP MU / Nextgen & PhotoQ integration

Hi there,

I tried both Nextgen and PhotoQ image galleries plugins and got the same kind of errors in both cases when trying to upload images...
With Nextgen it first read

ERROR: dosbook 002.jpg :
Fatal error: Call to undefined function: wpmu_enable_function() in /homez.63/brikabra/www/wp-content/plugins/nextgen-gallery/admin/functions.php on line 841

Then (despite confirmation that the upload was successful) :

Directory /homez.63/brikabra/www/wp-content/blogs.dir/6/files/1series contains no pictures

I got the same kind of messages when attempting to upload images with PhotoQ (which doesn't seem to integrate well...).
The files actually are on the server... yet the directory wasn't created.
Anything to do with the permissions on the blog.dir (at the moment 755)?
Anyone with a possible solution?
This one is critical since i would like to be able to host photoblogs..

Thx in advance.
Annabel