I discovered this on four domains a few months ago. I corrected the problem, then contacted enom support. Their reply? "They are currently set to the nameservers you want" Of course, since I put them back, duh. They said that they had no means of finding out what led to the wrong settings. BS, I say - everything should be logged. After the incident, naturally I double-checked all the domains in my account, and determined that there were no more problems.
Then early this week, I found the same thing on four more domains; three of them were .info domains that had the correct settings since the free .info promo, which is still less than a year ago, so there was no expiration involved in this instance. No use contacting support, so here I am posting about it. Best make periodic checks of all your domains, people. You never know. And if this keeps happening to enough people, and document it properly, then maybe we *can* consider that class action suit.
Hello enom, are you listening? This better stop.
As if the Big boys don't make enough off of us as it is ....... 
