Hello everyone For about a month now I noticed that whenever I'm watching a video on YouTube in HD or when I'm watching a movie trailer on Quicktime at 1080p, the playback lags. Prior to this everything worked well. All the videos I watched played smoothly at any resolution at any quality. I have an iMac with the following specs: 2.4GHz Intel Core 2 Duo 4 GB of DDR2 SDRRAM ATI Radeon HD2600 Graphics Card with 256 VRAM Also, I do not have many windows or applications open when I watch these videos. I have also close to 21GB of hard disk space used up out of about 280. Are there some applications for the Mac that can free up video memory or speed up video playback. All help is appreciated.