Quick version: If you’re having problems with ‘svchost.exe’ stalling your computer at Windows startup, it’s possible it can fixed by disabling Microsoft Update, at least until a fix is released. This can be done by going to the Windows Update link in Internet Explorer, selecting ‘Change settings’ on the left, then running the the uninstall option at the bottom. This still allows automatic downloading of standard core Windows updates, but not for Office. This is not the same as disabling all Windows updates in the control panel, which is a bad idea. I’ve used this fix on three computers in the past day and it’s fixed the problem on them all.
Longer version: For a few months I’ve been seeing computers stall at Windows startup (and other occasions, such as when loading IE) for minutes at a time. Mouse-clicks stacked up and were run all of a sudden once svchost decided it was done chugging. The task manager revealed only that ‘svchost.exe’ was taking up 100% of the CPU, which was unhelpful. ‘Svchost’ is a generic container for Windows services – the background programs that *should* be of little interest to the average users. A little investigation (I got sidetracked by thinking it was linked to iPods for a while) and some googling finally turned up links to this Microsoft KB article, which accurately describes the problem. The high cpu usage is apparently caused by the Windows Update service, and seems to be widespread. A few forum posts indicated it was Microsoft Update causing the problem: MU is an optional upgrade that monitors Office (and other Microsoft programs?) for updates, rather than just the core Windows files monitored by the standard Windows Update. The WU website asks if you want to install MU on every visit, and I expect many people have (I do by default).
Microsoft apparently have a hotfix for the issue, but are still testing it for public release. I hope they get a move on – there must be people who’ve spotted that the problem started after they enabled updates, so have simply disabled Windows updates entirely in the control panel. You can live without automatic Office updates for a while, but core Windows updates are just too important. It can be hard enough convincing people to turn on automatic updates in the first place, too.