Pk_campaign not working (vers. 1.12)

Hi Matt,
since we moved from 1.9.2 to 1.12 campaign tracking is not working any more.
We examined all suggestions exposed here: Troubleshooting - Analytics Platform - Matomo
but none of them seems to cause our problem.
Page views are regularly tracked, which we actually see in the Visitors Real-time and in the Visitor Log tabs.
We also note that the pk_campaign parameter is absent in the piwik_log_action table and in the
referer_url field of the piwik_log_visit table.
We made our tests with different browsers (IE8, Mozilla, Chrome) and,
as a typical example, we used links like the following:
Aeroporti — E-R Mobilità
In the same page you can obviously take a look at our tracking code.
Can you give us some suggestions in order to debug this problem?
Thank you.

Upgrade to latest Piwik 2.0, this should work. See also Visits from search engines or campaigns are not recorded, Piwik shows "There is no data for this report" for all Referrers reports. - Analytics Platform - Matomo