If you own a Garmin Zumo 550 or earlier your gonna start running into these problems. Just last month the buttons popped out, what to do? After searching the web a couple of ideas came to light, I could buy replacement button pads off this guy in the UK for around $70 or follow the direction of another fellow. I put the $70 back in my pocket and got ahold of an old remote control, you can use a calculator as well. Cut the buttons off that you want and glue them in place. The trick is to get the right size buttons and the right glue. Most all buttons are silicon rubber and marine glue or silicon glue just will not hold. You need LOCTITE 401. No need for a primer, a small dab will do ya because it is like crazy glue for silicon rubber.
Also if your touch screen goes bad and your cannot move around it's probably because the digitizer went bad. Best idea is to buy another digitizer off Ebay for $10. I originally ordered a full screen assembly replacement $40 but it was the wrong size, shipped it back and it was lost in China. It's not like replacing an iPhone screen where a full assembly is best. The digitizer screen on the 550 is easy to remove and replace, take your time and be gentle, you'll save big $$.
Last and most frightening was a power loss, most talk on the internet is replace the cradle, if you can find one. No way, I went as far as cracking the power cradle open and inspecting and cleaning everything, and checking my solders as I have the cradle directly wired to my 12v outlet. I found this write up in another Form and it saved the Zumo from the auction block. See below

I had a similar problem w/ my Zumo 450. Attach your meter to a known good ground. Probe the 4 holes w/the positive probe. if you don't get power then the problem is in the cord or at the fuse. If you get power then leave the probe in that hole and disconnect the ground and probe the remaining holes. If you get power then the cord etc is good. If you don't then you have a bad ground. Let's say you have power to this point. Reconnect the power cord to the cradle. Reconnect your meter to that known good ground and probe the 24 pins for power. If you don't get power then the cradle is bad on the positive side. This where i found my problem. If you get power then note that pin, disconnect your ground and probe the remaining pins while touching the power pin to see if you get power. No power then the ground circuit in the cradle is bad. If you get power then the problem lays w/ the unit. Follow the directions in the other posts. Maintenance wise I always keep my connections clean and use a lot of di-electric grease to seal water and crud out.
Hope this helped ~Harvey

Big Thanks to Harvey, turned out it was my ground, I cleaned it up put some electrical grease on and now I'M in business. Only thing left is to call XM radio and get the free three month trial. Hope this post will help.