I've been running Media Center for many years, and I've never encountered this. I have received this multiple times since I installed MC 32. The thing is, I'm running it under the administrator account at the moment, and it still displays the attached message: "This version of Media Center must be activated by running it once with at least Power User privileges." But it's running under Administrator right now, and it still gave me the message. It's referencing a file called MJTSFileWriter.ax. I did find a thread back on MC22 about a similar error message that said you had to play some live TV before the file gets registered. The error message certainly doesn't make that clear.
I did just play some live TV using both my ATSC 1.0 and 3.0 tuners, so will this properly register the required files and the error message goes away? I normally only use MC for OTA recording (which is working fantastic by the way)