Microsoft has rolled out a couple of hotfixes for the Windows 10 Technical Preview build 10049 tonight. Between the two, the hotfixes address an issue preventing users from enabling Hyper-V after installing build 10049, as well as an issue with Outlook preventing the client from indexing new emails.
Here's the full description of the issues each update corrects.
After installing Windows 10 Technical Preview Build 10049, Outlook 2013 and Outlook 16 Preview might not index new emails. As a result, new emails do not appear in search results, and if you rebuild the index, no emails appear in search results.
You cannot enable Hyper-V after performing a clean install of Windows 10 Technical Preview Build 10049, nor after upgrading to Build 10049 from a build that did not have Hyper-V enabled.
If you're running Windows 10 build 10049, you should be able to snag the above hotfixes from Windows Update now.