Thanks for the tip on the cache settings.
But, it's still not working as anticipated. I left the site for two days, working on other projects, then came back to the site, and no banners displayed at all. Upon refreshing the page, I get one banner zone to display an ad, then on the next load, a different zone will display an ad, then none, then two, then none, then none, then one, etc...??
Sorry for the noob questions here, but there must be some other simple thing I've missed somewhere....?
any ideas?