According to another forum:
"today i have received this reply from amiko support:

Unfortunately YouTube has changed their API service without any notice.
This is why your receiver is currently unable to play any videos.
We are going to release a new Spark software to fix this issue, hopefully next week.

The situation is also similar regarding the Weather Forecast service, however unfortunately the Google Weather API service is no longer available.
We are currently looking for another Weather Service to implement, however unfortunately I can't let you know any exact information regarding the time."

Good explanation, right on time, before ruining my STB on testing, or visiting a shrink; so don't blame Spark, blame Youtube...