Very suspicious that it mucks up Opera. (Curious, you use Firefox as well?)

I turned off automatic updates; I like to wait 'til others have had a chance to discover any problems. I'll wait for you to tell me when it's safe. Meanwhile, System Restore?

The latest patches were to correct vulnerabilities (RCE) in Excel and MS Movie Maker.
Possibly some help here: A simple fix for Microsoft Update problems | Tech of all Trades | TechRepublic.com

On March 5 Opera announced a vulnerability, caused by a buffer overflow error when processing malformed HTTP "Content-Length:" headers. By exploiting the vulnerability an attacker could make the browser crash or execute arbitrary code by tricking a user into visiting a web page hosted on a malicious web server. Affected are Opera 10.50 and earlier versions. At the moment, there is no patch available, though developers hope to have one very soon. Opera users should avoid visiting untrusted sites and clicking dubious links. Opera still claims to be the fastest browser for PCs, and recently noted three times as many downloads following the new MS Options menu available in the EU (allows users to choose from among a list of browsers).