"did you register with Silicondust all of your devices " I'm not sure what you mean.
When you subscribe to EPG from Silicondust, they tie your subscription to your device IDs. I was just wondering, in an unlikely event, whether they only tie your subscription to one of your devices, and at the time you tried, only one device was available, and that one happened to be not tied to your subscription. Obviously if at the time you tried getting EPG both devices were seen by MC, then the issue is somewhere else.
The error message "Failed to download EPG data from SiliconDust, Error: unknown" just means exactly what it says, MC failed to download data. MC submitted your Device IDs to Silicondust, but could not get EPG data.
Turn on logging and email me a log of this failure.