I also believe deleting the SoftwareDistribution folder will fix this as Saltgrass mentioned. "sfc /scannow" should stil be ran first however..
The proper procedure in doing so is as follows:
1) Stop "Windows Update" service
2) Stop "BITS" (Background Intelligent Transfer Service) service
3) Delete or rename the SoftwareDistribution folder found in your Windows folder
4) Restart the services we stopped earlier
5) Retry Windows Update
You may also be having issues with the cryptsvc,
1) Stop cryptsvc service
2) Navigate to Windows\system32 folder and renane catroot2 folder to catroot2.broken or something simular
3) Restart cryptsvc
4) Retry Windows Update