2007WFP - lines appear when specific Excel file is opened

When opening a specific Excel (.xls) file using my new Dell 2007WFP flat panel monitor, strange lines appear all over the screen. They even appear outside the Excel window, on "top" of other programs or the desktop. Minimizing and maximizing will make the lines go away temporarily. I have not experienced this with any other files. The file in question was created on my work computer (which also uses a Dell flat screen, but a different model) and did not exhibit this behavior at all. If Excel is minimized, there are no lines at all - but they are annoyingly persistent when it it opened, whether full or partial screen.

 

The lines are repetitive in about 8 columns across the screen, each about 1 cm in length and in pairs, with one slightly higher than the other. Hard to describe, but you get the idea. It must be some kind of display issue, but I don't know how to resolve it. I have the latest driver.

 

Any suggestion as to why this is happening?

Thanks,

Eric in Spokane