Mac Pro 2008 2.8ghz dual quad core 10gb 800mhz DDR2FB DIMM memory OSX 10.6.8 & 10.7 I have an intermittent issue whereby when I plug devices into the USB sockets (front or back) other USB devices are disconnected and I get the pissy message that I have disconnected a drive without putting it away first. Sometimes the disconnections are spontaneous and don't require anything to be plugged in. I was advised that this could be a USB device attached or the logic board. I minimised USB devices, ran machine with nothing but keyboard and mouse and not the original ones. Problem still occurred. Bought an identical mac. Stuck my hard drives and a couple of gig of memory from the original machine in it. Problem reoccurred initially then went away for three months. It has just returned and appears to be specific to one 500gb USB powered external drive. Memory sticks and cards do not have the same effect. I have a card reader and a USB hub previously used on my old mac plugged into the new one. Also, I had the old mac with the drives a swapped out ticking over with every usb card and stick I had spare attached via the subs and the above mentioned hub for a while to try and reproduce the effect. Nothing ever disconnected. Lastly, one of my drives has 10.7 installed and the fault occurred when using that version of OSX in the old machine. Have not run it for any length of time in the replacement machine. With an intermittent fault that can have months between occurrences how the hell can you test against every possible cause? Any thoughts out there?