Alex,
NGG 1.7.4 worked fine with WP 3.0.5 for me, and still works mostly ok: I’m able to generate new galleries, download photos etc. But there are still some challenges:
1. When downloading new photos – all of them far below 2 Mb limit – the generation of thumbnails succeeds with some photos, but not with all. I have no clue why some thumbnails generate ok, since there are not obivous differences in photo size or content.
2. Maintaining thumbs in admin mode does not seem to work, even though the thumbnail editor states “thumbnail updated”.
3. All photo galleries I now have display thumbnails ok, but with both Firefox and IE 8 most photo galleries stop loading full photos after two or three shown photos. Individually selected from thumbnails any photo loads fine (either as a slideshow in the page or PicLens).
I use Atahualpa which has so far been working perfectly with NextGEN, as well as NextGEN Gallery Sidebar widget, still working fine.
I understand there could be a problem with the web hotel operator (e.g. with cacheing), but most likely it seems to be some kind of a compatibility problem with WP 3.1 and NGG 1.7.4, as many previous comments also seem to state.
NextGEN is an excellent tool and I sincerely hope these issues can be solved.
Thanks for trying anyway!