I have a server that uses a third party disk encryption product. It’s configured so that the SQL service account and sysadmins have the ability to encrypt/decrypt files. The local system account does not, nor does the local admins group. Good for security, but it causes some pain when you run a service pack. Service packs extract and then run the installer under the local system account. With my setup the files extract successfully (running as me), then hangs while local system tries to access what are to it in encrypted files before finally (a long wait) failing. The solution is easy enough, just extract the files manually to a drive without encryption. The way to do that is with the /X switch. For example, if the plain text drive is Z, you’d use something like /X:Z:\servicepack. Details at https://technet.microsoft.com/en-us/library/dd638062(v=sql.110).aspx.
Noting it here because the error message isn’t helpful and searching for command line switches will usually land you on https://technet.microsoft.com/en-us/library/dd638066(v=sql.110).aspx, which doesn’t show the /X option.