If you're running other (memory) 'heavy' mods, you might want to temporarily disable them and then try to replicate the issue with New Interiors.
Also, there are a number of 'fixes' available that make other mods compatible with NI, so you may want to check your mod list and see if there are any potential conflicts.
Aside from that, Bakkels is quite correct in suggesting you may need the 4 GB patch (along with the corresponding amount of RAM) in order to successfully run it.
Good luck!