@Don - What version of NextGEN Gallery are you running? Would you mind upgrading to v1.9.13 and see if that fixes it? If you are running v1.9.13, you might try refreshing the plugin files and see if that helps.
Is this a consistent issue with multiple slideshows? Or just this one? One other thing you try is switching your permalinks to 'post name' under Settings >> Permalinks. And under Gallery >> Options > General Options > select 'activate permalinks'.
Hope that helps!
-Becky