Microsoft has not seen a ton of issues rolling out its April 2018 Update for Windows 10, though there have been some snags along the way, prompting the company to block the update on some machines. We saw that recently when Microsoft halted the update to machines running an Intel SSD 600p or SSD Pro 6000 series drive until a fix could be issued, and now we're seeing it again, this time on systems running Avast's antivirus software.
Over on Reddit, it's noted that several Avast users have experienced trouble trying to install the update. Affected systems would boot to a blue screen asking the user to choose a keyboard language, after doing so, they would be presented with three options—Windows Rollback, Windows 10 on Volume [X], and Windows 10 on Volume [X]. Yes, two of the options are identically labeled, and choosing either one would take users to a blank desktop with no icons, and an error message that the Desktop file could not be accessed.
Microsoft and Avast are investigating the issue, and in the meantime, Microsoft is actively blocking the April 2018 Update from installing on potentially affected systems.
"Microsoft temporarily disabled the updates on version 1803 on PCs with Avast. We are working together with MS to find out the cause of this issue, but unfortunately right now neither MS nor us are able to reproduce the issue," an Avast team member said on the company's support forum.
If you're running Avast's security software and don't want to wait for Microsoft and Avast to figure things out, there is rather simple workaround—you can uninstall Avast, apply the update, and then reinstall Avast. It's obviously a bit of a hassle, even more so if you have malicious files sitting in quarantine. But it appears to be working for folks who have tried that method.