Different domains and content but same ads displayed - help

[Alminc]

Hi guys,

I installed two sites on a same cpanel account, hostgator 'baby'.
Each site has its own addon domain, different domain name and
different content (completely different topics).

However, ads displayed on a second site's homepage are
same as for the first site. I don't understand why it is so.
I even used different ad units.

site A: domain name A, content A, displayed ads A

site B: domain name B, content B, displayed ads A


Can it be because the sites are built on addon domains?

Anybody had this problem? What to do?