It was August 2009, the problems eventually led me to this forum, which fixed everything so I gratefully joined as a paid lifetime member.
In a nutshell, I found that when the CH is too high, and the air temp is 115, aerating at night to keep water temp down... drinking acid like crazy because of the aeration and salt water chlorine generation, even though PH, CYA and everything else is right, brushing the pool daily etc, I started to have a black algae problem. Small spots appearing here and there. I did battle daily. Followed pool store recommendations and tested water there a couple times a week! Shock, scrub, rebalance everything then it started all over again a week later. Pool store just took my money and sold me everything under the sun!
SOooooo frustrating!
But I found this website, bought a test kit and all has been well since the end of 2009. I do test and indeed 2 years is about it, so I automatically plan on draining in even years.
In hindsight and subsequent dealings with the company that built my pool and owned the pool store I feel that they put sales ahead of what is best for the customer. I can say much more on this but not in a public forum.
Anyways, I am very happy with all the help and mostly sound advice that can be found here, and pleased to report I have had no chemistry problems since joining.