delete query taking way too long

I've
delete from catalog_items where ItemID in (select id from
import.Articoli_delete);

id and ItemID have an index.

catalog_items is ~1M rows
Articoli_delete is less than 2K rows.

This query has been running for roughly 50min.
Right now it is the only query running.

PostgreSQL 8.3.4 on x86_64-pc-linux-gnu, compiled by GCC cc (GCC)
4.1.2 20061115 (prerelease) (Debian 4.1.1-21)

--
Ivan Sergio Borgonovo
http://www.webthatworks.it