In Windows 7, the Notification Area has a little chevron icon (a vertical-pointing triangle) that you click to show hidden icons (like the Volume or Network etc).
Over a period, I noticed that the chevron would overlap the first visible icon in the area (typically the Action Centre Flag icon) and no matter how you tweaked the icons from hidden to visible and back again, the chevron kept overlapping the first visible icon.
Then a mention of the “Notification Area Icons” under Control Panel (in an internet search) took me again to the familiar “configuration” window. However, this time I noticed the unticked box “Always show all icons and notifications on the taskbar”. So, after ticking and OK’ing that, there was now just a string of icons (not including the original chevron button, of course).
Back to the Control Panel, unticking the above-mentioned box and amazingly, all the icons are now spaced correctly with no more overlapping.
Unfortunately, it is not a permanent fix. A reboot or moving the Desktop Toolbar will un-fix it again. Grrrrrrrrrrrrrrrrrrrrrr!