These are issues with hardware accelerated drawing. Turn it off in the prefs and/or update your graphics driver.
Thanks for the quick reply, my graphics driver is up-to-date and I did turn off hardware accelerated drawing as you suggested, made no difference
I think you may have misunderstood the problem, all screen drawings look fine, the 'Marching Ants' I referred to is the standard user indication that crop mode, or other selections are active.
The actual display looks fine, the problem is that PS enters the crop mode when it shouldn't do.
In my experience, after using the crop tool on an image, it will still be active when you choose another image to work on. I just hit the letter for a different tool and it will be gone, but the new tool will still be active when you load another image. Seems like the tool is sticky and will remain until changed. However I haven't considered this to be a bug or any thing like that. I just hit the M key for rectangular tool and all goes away. Others may have a better answer I am sure.
I would agree with Billnor. I always just select another tool, unless I want to crop.
The poroblem is that the crop tool is active even if though I havn't used!
For example, let's say I have several images just opened and the current tool was the Crop tool, but I havn't used it. When I open a new image, the crop tool becomes active with the crop area showing. If I Ctrl / Tab to the other images each one wil now show the active Crop area, even though I havn't actually used the crop tool.
I've discovered that I can use the crop settings to switch back to 'Classic' mode, and that doesn't exhibit the problem, so I'll stick with that (the 'Classic' mode seems more intuitive anyway).
Thanks for your reply though.