I rent my spark out typically on the upxplorer website that was created through the House of Spark service.
Just recently Upland however converted Spark in-game to Sparklet in advance of the link to the ethereum exchange and in doing so it looks to have broken this service because my account balance is running up in a wild way that it shouldn't and says that I have an account balance of over 400,000 upx right now.
I never really have more than like 1,000 - 2,000 upx in my account so this is an obvious. I did my part informing to House of Spark team so hopefully someone fixes this soon because I can't continue to use the service if I can't withdraw anything from my account...