An event driven script in a spreadsheet opens another spreadsheet

```
var ss = SpreadsheetApp.openById(otherSpreadsheetId); 

```

Looking at the execution transcript, I get the following error

> 
> SpreadsheetApp.openById([0AjqSnE\_p3nFqdDN0LWpFbjFqVDRwNmFGOV91QzZrZc])
>  [0 seconds] Execution failed: You do not have permission to perform
>  that action.
> 
> 
> 

When I run the function directly in the debugger, I successfully open the other spreadsheet. When the function is run by an "onEdit" event, then I get the error.

Do I need to enable a particular API?