I have spent about 3 hours reading all of the posts on this subject, tried as many of the "fixes" as I could understand (including the hacks) and I cannot get nexGen to work on a multi-site install.
I am running 3.0.5 multisite enabled
NextGen gallery 1.7.3
I have tried network activated and allowing the individual site to choose to activate. The gallery works fine on the base site but sub sites get this:
NextGEN Gallery : Tables could not created, please check your database settings
I really like this gallery but cannot figure out how to use it in a multi-site environment... anyone?