Microsoft recently released an update to fix some Explorer.exe crashes in build 9879 for the Windows 10 Technical Preview. For those that could get it installed, the update helped stabilize the beta operating system. But, there were some (Microsoft says only 12%) that couldn't get the update to install at all, leaving them stuck with two problems: a constantly crashing version of Windows 10 and the inability to get updates installed.
Microsoft has since delivered some guidance on how to get the update to install successfully. Gabe Aul, the Windows Insider chief, wrote up instructions and handed them off to be posted in the Windows 10 Technical Preview/Windows Update forums on the Microsoft site.
The workaround involves running a command in the Windows 10 CMD window and the promptly rerunning Windows Update. You can find those instructions here: How to install Windows 10 Technical Preview Update KB3020114
Gabe also goes into detail on why the problem exists. It culminates from two underlying bugs, both having to do with System Compression. However, I can think of an even better reason: it's beta software.