EIG is particularly fiddly, but I don't usually do "save as" or take files out, I have a bunch of store content and mods, and I haven't had any trouble using it.
A couple of things I know that cause problems with CAW/EIG:
1. If you have a "go social" (post 2012) Sims 3 base game - it's not compatible with EIG if I recall correctly.
2. If you have patch 1.69 (the latest), there's an updated CAW specifically for that so that EIG will work again (the patch from 1.67 to 1.69 caused EIG to crash in the original CAW).
If you have a pre-2012 base game and the CAW that matches your patch level, I'm not sure what could be causing the issue :/
And sorry if you knew all of this already, I didn't want to make any assumptions!
@Rflong7 can probably help you! (I'm a new member, so not sure if it'll tag her properly).