Google docs and the Eve central API for data has not been playing nicely.
I wrote up my implementation of a solution based on Steve Ronuken's google script fix, that works moderately well.
The problem I had is that Google was caching data for far too long, and I missed some price changing trends.
The solution is to use a ?cachebuster=<value> parameter when you want a new call.
From the Eve Central API, apparently we are allowed to pull the same data every 5 minutes. ( https://groups.google.com/forum/#!topic/eve-central/b5FjssiqFIQ ).
For my purposes, I don't care about completely current pricing, and price refreshing makes my spreadsheet unusable for about 30 seconds while it happens. My current solution is to pass the day of the month as the cachebuster parameter, that is I request different data once per 24 hours.
I will be keeping a bit more of a closer eye on this as PI prices have moved around a bit over the last few weeks (post scheduled for Tuesday my time).