My bottom row of icons moves up one row whenever I extend my desktop. How can I get my bottom row back?

None of the MVPs from Microsoft's support forum could help me. At any rate, I am running Vista Home Premium Service Pack 2, and my display drivers are up-to-date. The problem only occurs when I extend my desktop to a monitor on the left side of my pc. I cannot move the icons back to the bottom row except on my second monitor and in the very bottom right of my main monitor. Weird happenings...I know, but thanks for any help you can give.