In Excel 2003 why does ctrl+v paste an image of the screen instead of the
previously selected and cut cells?

If I select a cell or number of cells, use ctrl+c to cut then move to the
area of the sheet where I wish to paste the cells (problem only occurs when
moving using the cursor keys) using ctrl+v to paste results in pasting an
image of the screen rather that the previuosly selected cells that were
copied to the clipboard.

Using ctrl+c then moving to the paste location by using the mouse result in
the ctrl+v paste working as expected, but everything goes wrong when using
the arrow keys to move between the copy and past operations.

I have no macros defined within this or any other of my Excel spreadsheets,
so cannot understand this problem. Please help!