Debugging output visible

I am seeing the following spurious output on the very top of my pages:

Array ( [0] => http://my.site.com ) Array ( [0] => http://my.site.com ) Array ( [0] => http://my.site.com )

I believe this is somehow related to elf, as it appeared right after upgrading to 3.0-alpha1, and disappeared after downgrading to 6.x-2.1. Please change issue Category as required. I am running several other contributed modules (namely domain and views) on Garland theme.