How to create a Pie chart using views google chart tools
I had the issue - though not in drupal, but a native php application. While I've read that large differences in values can trigger the "other" slice, this was not the case in my application.

The datatable rendered perfectly as ColumnChart, but failed to show slices as PieChart and only came back with 100% "other".
What resolved the issue for me was casting the values in php to integer with intval().
Apparently the CulumnChart visualization is forgiving, while the PieChart is not when it comes to values other than intergers.
Hope that helps clarify.