My eXplorist XL just came up with this problem (for the second time) today, too. I have already had it repaired for this issue once (according to the tech support idiot I ended up on the phone with, the display was replaced). It has never gotten wet, so I can pretty much guarantee that this is not the problem with mine.
I am supposedly getting a prepaid shipping label via email for the return this time, although it has not yet arrived after two hours, and a call back from a supervisor to discuss further options. I'm giving them until Monday before they experience my wrath!
I've been cruising the forums both here and at the GBA to see if anyone else had this problem with a Magellan unit -- so far, you're the first I've found (other than me, that is!)... I would appreciate finding out what they tell you about getting yours repaired, as I expect that this will be a recurring problem with mine, and it would be good to know what they're gonna want to soak me for once the warranty runs out this summer.