So today, my MacBook Pro (Late 2011, 17-inch) is acting strangely. The mouse is all jittery and everything runs slow. I check the activity monitor that shows 1200% cpu! The battery has an X across it and said "battery is not available". I did an SMC reset and the battery was briefly detected before going back to an X. Reset NVRAM didn't help. I disconnected the battery and reconnect it after a minute. The computer runs normally for now. Cycle count: 776 Is this a real issue or a one time glitch?