The DynamicsBlogger has a great look at Excel Report Builder and how Publish Report in GP 2010 including information about security needed to publish Excel reports.
DynamicsBlogger: Excel Report Builder–Publish Report in GP 2010
Reporting & BIGP 2010
Archived post from 2011. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.