SQL Server Agent: QUOTED_IDENTIFIER
I just ran into this same issue. By default the first statement in a job step is to SET QUOTED_IDENTIFIER OFF - you can see this in a Profiler trace. The solution is to add a line at the beginning of your code to SET QUOTED_IDENTIFIER ON.

As to your script not containing quotes - I believe when creating or rebuilding certain types of indexes that setting is required is to be on.

Here's a couple links:

https://stackoverflow.com/questions/15218893/first-statement-issued-by-sql-server-agent-sets-quoted-identifier-off