I've installed a new version of WSPR (4.0 r4171) and it's more stable than 2.21 on Windows 8. The old version would run for about 8 hours before stopping with the scary sounding Fatal Python error. This one has had no problems so far.
It can be downloaded from here
I've tried WSPR-X a bit but it doesn't have band hopping and that's something I use a lot.