Microsoft Insider Build 14376 has some changes that have caused issues with WindowBlinds 10.05.
We believe we have identified the issue and resolved it in the linked hotfix
If you are running the fast ring of the insider builds and have experienced the issue (a black screen) you can restart in safe mode or hold the [Ctrl] key down to disable WindowBlinds.
Once you have access to your desktop, you can install the beta from http://sd.stardock.com/zubaz/WindowBlinds_10.0.7_beta_setup.exe
If you are running the slow ring (or the fast ring and have not experienced the issue; now is a good time to update.
Windows 7 and 8 are not affected by this issue. Installing the update will not adversely affect those operating systems though.