Thankfully I've not experienced this issue, but I've read a fair bit about it. There's no hard proof of what causes it, but contrary to other views in this thread, my impression is that it is caused by infrequent switching, including leaving a printer dormant for an extended period. My recollection is that the automated switching process referred to by Farmer is not all that frequent. There are very few reports of people seeing it happen. A repair of the switch is costly enough to be only marginally economic at best. My view FWIW is that monthly or bi-monthly switches are fairly inexpensive insurance. After all, if we could just rely on the firmware to do the switch then these problems wouldn't be happening, but they do. I suppose it's possible that in response to the problem Epson released a firmware update that triggers automatic switches and the problem doesn't occur in printers with the updated firmware, but that's unproven and I'd still prefer the inexpensive insurance of moderately regular switches to a costly repair. The fact that there are some people who have switched only infrequently and haven't had the problem only proves that it doesn't happen to every printer, and is no guarantee for yours.