On a Mac? Excel running slowly for you? Copying four cells causing a beachball? Have a clipboard manager (e.g. PasteBot, or BetterTouchTool)?
Turns out, in Excel, when you copy something, in addition to copying the text data, Excel also generates a picture. While it’s doing that, it blocks the clipboard manager, causing the beachball. Found this info on a BetterTouchTool user forum post, but it equally affects my clipboard manager of choice, PasteBot. I’m guessing this also affects any other Office application (e.g. Word), but haven’t tested it — just added both Excel and Word to the Pastebot exclusions list. I’ll gladly take the loss of clipboard history for the increase in speed — nothing more frustrating than having to wait on your brand new computer.