Thanks for the reply ATR,
The SSD capacity is 64GB, approx. 16GB free. I don't work with large projects (less than 5 mins runtime) so I didn't think that would be an issue - could be wrong though, as said before I am certainly not an advanced user. Only the scratch disks and the actual program files are on the SSD, all the projects and final video files are stored on the main disk (1TB).
I have checked those two file locations - the adobe folder under My Documents doesn't have a preview folder? Just a 'Styles' folder with one file in it, and 'session.log' file. The media cache file is also set to the SSD. Tried cleaning it, but no effect.
No playback issues at the moment, quite happy there.
I tried ccleaner, it picked up some registry issues, but didn't appear to have any effect on the issue. No issues with my computer yet so hope it stays that way.
Cheers for the clarification about the red line over the timeline thing. I had guessed it was something like that, but it's good to have someone knowledgeable confirm exactly what it means. As far as I can tell, the video files/project preset are correct then as it is doing exactly what it should per your description.
The issue is not limited to the - + timeline slider, it also occurs when trying to resize the timeline vertically (click on bar between playback window and timeline, drag up & down), minimising/maximising window, and a few other things. It basically seems as though whenever anything like that is done, the framerate drops to about 0.5 fps. It actually looks like I can see the refresh line moving up the screen.
I will try track down a different/older graphics driver per John's suggestion over the next few days and see if that makes a difference.
Cheers,
Avalanche01