I have an issue where my largish (11300+ rows) Excel spreadsheet has a problem sometimes when I use the mouse wheel. The mouse wheel won't actually move the sheet up or down as expected, but then when you click a cell it actually changes to a different cell that is several rows difference. If the window is resized or the scrollbar is used then everything starts working again with selecting a cell or even using the mousewheel. Note this looks similar to the "Under review" item of the mousewheel not working in Excel, but this covers more info about how it starts working again etc.