WordPress MU

Greetings,
I just upgraded to WPmu 2.6.2, using K2 RC7. I am creating a new gallery of images, I upload them in batch using the flash uploader (about 58 images) and I Insert the gallery into the post.

http://avatar.iamzaks.com/lang/es/zhao-de-la-tribu-agua-parte-1/

The images are not resized, a thumbnail is not shown, instead, the gallery shows the full size images and some of them in medium size. I tried the following tags on the post:
[gallery]
[gallery columns="3" size="thumbnail"]

I tries deleting the files and re-uploading, but to no avail.

Thanks in advance for your time and help

anyone? please help, this is kind of urgent, I need to publish that gallery

Is GD2 and/or ImageMagick installed on your server?

I don't really know, how would I check?

Ask your hoster