Mac Pro 3.1 2.8 GHz 8-Core - A1186 MA970B/A Early 2008 24GB RAM Wired USB mouse connected through Apple full size keyboard. Mouse and keyboard work perfectly on my other Mac Pro (1.1) running 10.6.8 and have done for years. Mac shows usual desktop after booting and usually results in the stuck cursor. Sometimes the keyboard and mouse have no power, other times they do. When they work I move the mouse 1mm and after a few seconds the cursor moves quite a large distance across the screen (the cursor also sometimes disappears and reappears somewhere else). When I try to input text one keystroke results in 7 x that character autofilling. Means I can't sign in as admin to try to sort this out. If I try to click on any finder menu it drops down and immediately disappears so can't select anything. I've only had this mac for 2 days during which it worked ok. After connecting to the net for the first time I opened Chrome and about 5 small pop up windows appeared. I just closed them without thinking but later thought they may be malware or a virus so I then downloaded Avast free for mac and did a scan. The next time I booted the problem started and have to hard shut down everytime. Things I've tried: 1. PRAM reset 2. Reset SMC 3. Safe mode restart 4. Unplugged all leads before booting again. 5. Connected mouse direct into mac (every USB port). 6. Used another wired non mac keyboard. Message then appeared saying bluetooth keyboard could not be found! 7. Looked for hours online for a solution! Any help appreciated. Update - Deleted Avast after starting from external HD but cursor still not working properly. Very small movement of mouse results in a large movement of cursor after about a second delay. Keystrokes still autofill 7 times and can't select from menus.