Explorer and Network drives, path auto-collapses

Has anyone noticed that if you have an Explorer window open and you've navigated to a folder a few levels down and on the left, the path hierarchy is displayed in the normal way, but if you switch to other windows and don't look at it for a couple of hours, when you switch back to it, sometimes the path hierarchy on the left has collapsed like in the screenshot below. You see in the top address bar that I'm 3 levels in and you can see the contents of that folder in the main client area. So if I want the path to re-appear, I either need to click on that Z: drive and then click Transfer and then Customizations and then Wallpapers. Or what I usually do is click the UP icon and then the path hierarchy magically re-appears and then I click the BACK icon to get back into the folder I was in.

It's not the worst problem in the world, I know that, but was just wondering if others had seen this and maybe there's even a way to stop it happening.