I am using a Logitech K750 Solar Powered Wireless Keyboard which uses a USB transmitter not Bluetooth. I am using it with a late 2009 iMac with 8GB of Ram and OSX Mavericks. It wasn't always this way but for some time now, when I type I occasionaly get a delayed response to my keystrokes, including the dreaded "spinning beachball." It takes a second or two for the display to catch up to my input (I don't type THAT fast!) and this is quite annoying and disturbs my workflow. Originally I thought it was the Logitech keyboard that was the problem, but eventually they told me to try the original bluetooth wireless keyboard that came with the iMac to see if it happened with that too. IT DID! So Logitech is off the hook. Does anyone have any idea what might be causing this problem? I have 8GB of memory and tons of hard drive space, so I doubt either of those are an issue. Does anyone think it could be a wireless issue and if I got a USB chorded keyboard the problem would disappear? I guess I will have to try that but since the bluetooth keyboard came with the iMac, it should work even though its wireless. If anyone has an idea here, I'd love to hear it. Thanks.