Microsoft Security Essentials hangs during a full scan

First off, can I be clear about one thing – endpoint virus scanners don’t make your computer “secure”. A lot of the most dangerous stuff gets past them, but trusting lusers believe they’re safe and will therefore take risks they outerwise wouldn’t. See my posts and academic papers passim ad nauseam. Now that’s out of the way, I favour Microsoft Security Essentials (or Microsoft Endpoint Security) on Windows as I find it less likely to make the system unusable. I don’t recommend it, except as the least-worst option.

On with the problem…

Sometimes, especially in the last year or so, I’ve found Security Essentials will stall when its doing a background scan. You may not notice its done this, but some symptoms are that web browser file downloads won’t work (it’ll download 100% but never finish) and the PC won’t hibernate automatically using the power-saving settings.

I’ve looked for solutions to this, as well as searching the web for an answer. You’ll often see people posting (without references) that this is bug and Microsoft are working on, or have now fixed it. I’ve tried theories myself to see if it’s caused by compression or archive formats causing a decompresser to break (I’ve noticed this often fits the facts), but this is little help when finding a solution, and even then it sometimes still hangs when the option to check compressed files is turned off.

What I’ve yet to find is anyone giving a real solution, so here it is:

  1. Deinstall Security Essentials.
  2. Download and install Security Essentials.

I’ve never known this not to work. On the other hand, I’ve known all the other theories you see posted on forums fail to work pretty consistently.