Hi there,
NextGen’s (disastrous) 2.0 release broke nearly a hundred plugins and themes, including some really large ones, like bbPress, W3Total Cache, and Events Calendar.
Unfortunately, this is due to some really poor code in NextGEN. As such, there’s only 2 options I can really suggest.
The first, is you can wait until they finally get to a stable version of 2.0. Since 2.0, they’ve released 7 updates (and counting) to try to fix all the issues the 2.0 update caused. Based at the length of the list of “known conflicts with 2.0” my guess is that it will be one or two months till they fix all conflicts.
I would recommend opening a ticket on their support forum. They are already aware of the conflict, but a little push always helps the cause I suppose. You can open a ticket here: http://wordpress.org/support/plugin/nextgen-gallery
The alternative option is you can rollback to a pre-2.0 release of NextGEN. If you are planning on launching a site within the next 2 months, or the site is already live, I would recommend “rolling back” until they fix all the 2.0 issues.
They made a rollback guide here:
http://www.nextgen-gallery.com/how-to-rollback-a-version/
In step 1, you would pick a pre-2.0 release.
One thing to remember is not to delete nextgen from your site. Doing so will delete the data in the database used to make the galleries.
Let us know if we can help or answer any questions
-Chris