Inaccurate Marquee tool

Question

I've recently upgraded from Photoshop cs3 to cs5.1 and have noticed that the marquee tool's selection is not as accurate as I'd like. For something simple like drawing a selection around a square I could previously do this down to the exact pixel with a single click and drag. My process (while working at 100%) now goes like this:
i) Choose which bit of the cursor I place in the top left of the square to trace (I use the black inner lines)
ii) Click and begin dragging and see that the selection in the top left is now 1 pixel down and 1 pixel to the right of where I clicked.
iii) Drag the selection to the bottom right of the square and align the inner lines of the crosshair
iv) Release the mouse button. The top left corner now springs back into the originally clicked position (good). The bottom right corner now jumps up to 2 pixels up and 2 pixels left of the actual corner.
I am left trying to approximate how far past my object corner I overshoot in order for it to be correct when it 'jumps' back. It feels as though I'm getting similar selection errors as if I was working at a random image zoom such as 337%
Anyone else experiencing this or more importantly know how to remedy it?
Thanks
Tech info
Mac 10.7.3
Res: 2560 x 1440
Photoshop 12.1
Notes
Jumping problem is the same if 'snap' is turned on or off
The problem occurs at 100% and is marginally improved at 200% - although I can't get an accurate selection in 10 attempts.
Also in cs3 the Marquee tool's crosshair was 1 pixel thick and now in cs5.1 it is 3 pixels thick due to the white outline around it, I find this harder to use and unable to switch off.
Selecting cursors 'precise' in preferences doesn't fix it

Answer 1

Trevor.Dennis wrote:
I tried filling a rectangular selection larger than the screen, and duplicating it free hand on another layer, but was one pixel out on two sides.  So I tried again at 200% and it was spot on.
This sounds like a similar effect, the requirement to zoom into the image in order to place an accurate selection. I've tried this repeatedly and the amount the marquee jumps is different each time, between 1-2 pixels up and to the left.
I'm trying to cut out many web type graphics which are only a couple of hundred pixels in height/width. Without an accurate selection tool at 100% my workflow is now:
i) Select Zoom and click three times to get to 400% (At which point selection becomes 90% accurate)
ii) Make the selection
iii) Double click the zoom tool to get back to 100% view
That is an overhead of five clicks which seems a bit long winded. Or I can re-open the file in Photoshop cs3 and select more accurately, which I don't really want to do.
Does anyone know of an option that can be toggled to make the Marquee tool more accurate or is a jumping selection on release just how it is?