In answer to the original question, no.
I am always surprised by the who-ha surrounding GSP failure modes given that NDBs (which we do rely on for non-precision approaches) have a whole host of known subtle errors and no possibility of integrity checking.
Don't get me wrong - I'm not saying there are not nor can there be any GPS errors. I'm just pointing out that we do already use something that is basically know to be unreliable at best an yet we get very excited about much less likely problems with GPS.
User errors are another story but don't get me started on that....