I was stationed overseas for a year with my RV-4 in the care of a friend. I never recieved my impending expiration notice. When I got back stateside, I recieved a new assignment and moved to Rapid City, SD.
So after the move I went online to update my address and was quite alarmed to discover that my registration expired MONTHS ago!

The support phone number on the website was perpetually busy. So I followed the instructions online to the letter--which informed me that once expired, you cannot renew a registration online.
The website instructed me to fill out and sign an AC Form 8050-1B, enclose a check for $5, and send to Oklahoma City. Then check periodically online to see when your renewal was approved.
Five weeks later (!) my daily website check informed me that there was a problem with my renewal. I immediately e-mailed the FAA per the website instructions, was pleased that they responded right away, but was displeased with the response. They told me that once your registration has expired, the 8050-1B is not appropriate and that I have to send in a signed copy of an AC Form 8050-1 (which I should point out asks for exactly the same information as the 8050-1B).
So I replied back and pointed out to them that I had followed web site instructions to. the. letter. Again, a surprisingly prompt reply informed me that they regret the error, they will fix the web site, and that I still owe them a 8050-1.
Lucky for me I kept two signed copies of the bill of sale from when I bought the airplane nine years ago. So hopefully I got it right this time and I'll be back in the air...in about five weeks.
BL: if you can at all help it, don't let your registration expire. And if you're going to be out of the country, make sure you're still getting your mail.
-Matt
402BD