Yesterday in my repair shop I started getting a 0x80246002 error when checking for updates. Only on Win 7, (8 and vista were unaffected). This first occurred on a customer box that had a malware infection. The KB for this error simply states:
This problem may occur if Windows Update or Microsoft Update determines there is a file hash mismatch when you try to search for available updates from the Windows Update Web site or from the Microsoft Update Web site.
I spent a couple hours down the rabbit hole, thinking malware had broken updates on this box. Not unusual, and normally fixable by one of several means. When all attempts failed, and then another box presented the same error, I checked, every single windows 7 box would not check for updates.
I found that it was not something strange in our router or firewall, and it even occurred on other building tenants computers using a separate internet connection. Everyone in the building is on Comcast. Even more interesting, if I connected a computer to another ISP (tethering on my phone in this instance), the update check would succeed. You could then reconnect to comcast and download and install the updates.
Further all of these computers were running Windows Update Agent 7.6.7600.320, which is a recent (KB less and not able to be skipped) update to Windows update, that you cannot roll back easily. However, by going to a restore point prior to this update, checking for updates magically worked again, until this Agent updated itself and it was broken again.
So somehow, for whatever reason, the way Windows Update on Win 7 with this version of the agent checks for updates was being blocked by Comcast (Business class). Try explaining that to a comcast support rep. Fortunately today it seems to be working again.