@Krista – I suggest you ask in the thread you are pointing to with your link.
No need to split the thread into two.
Now to your problem:
if all the pages end up in one spread it is no surprise that you get an error after page 10. The maximum page count of one single spread is 10.
Why do the pages go to one spread?
It's pure speculation, but I think it has to do with some preconditions your spreads are in.
Check for "Allow Document Pages to Shuffle" and "Allow Selected Spread to Shuffle".
Is "Allow Selected Spread to Shuffle" "off" or "on" for the particular spread where all pages are added?
And another question:
what is the particular script you refer to? There are a couple of scripts in this thread from various authors.
The original Thread is 3 years old, I didn't think anyone would read it, I'm sorry.
I'm using the script listed by [Jongware]-GfBROo although I tried all of them. They all do the same thing.
I have turned "Allow Selected Spread to Shuffle" on and off, as well as "Allow Document Pages to Shuffle"
I've determined that it's CS5 and something to do with allowing different sized pages. All of the scripts work as intended in CS4. Unfortunatly for me, I need different sized pages and therfore have to use 5.
@Krista – I suspect that goes in the category "Something has changed with CS5", a thread Harbs did bring to life back when InDesign CS5 was released.
We recently had a thread about problems with moving pages with different page sizes. This problem seems to be not solved yet. Not even tackled…
It would be good if you could provide the problem document, all pages empty, but otherwise unaltered, for testing.