Having trouble with objects do not exist error

Sounds like timing issues. Are you sure whatever you're using is allowing enough time for them to appear?

(Usually, the easiest way to verify this is to put an excessively long wait in before the action on the popup. If that makes it work every time, then you were try to access it too early and you need to put something in to detect it before you use it. I wouldn't use a wait permenantly. Hardcoded waits are never good ...)

Either that, or dodgy runtime identification properties.