I have had a search round the internet and it seems this is a common problem (going back to 2009 while W7 was being tested).
Lots of possible solutions given but there is always someone who says that "solution" did not work for them.
Suggest you search the internet for "Windows 7 does not refresh" or "Windows Explorer does not refresh".
You will find loads of "hits" and loads of possible solutions. Suggest you just keep trying the solutions till one of them fixes it.
Some possible solutions include old video drivers, network connections, Windows settings (Aero etc.) and many more.