http://www.techradar.com/news/windows-7-updates-stop-working-as-microsoft-takes-its-eye-off-the-ball

Some Windows 7 users have found that Windows Update has fallen over on their systems, meaning that they can’t receive any security patches or other OS updates.

So what’s happening here? Apparently, patches fail to download and affected users simply receive an error message when running Windows Update on their PCs. They are informed that an ‘unknown error’ has been encountered (helpfully) while checking for new updates, with the error code ‘80248015’.