It sounds like the gps is "crashing" due to a corrupted map file. I saw the same thing happen on my Oregon 400t a number of years ago while testing one of my own new maps.
First, just remove the card as Popej suggests. If it still happens, then connect to your computer again. Does the computer recognize the Oregon? If not, then try the recovery procedures listed in M3 here: http://garminoregon.wikispaces.com/Miscellaneous
When you can access the Oregon on your computer, delete the map that you just sent. It will be in the Garmin folder, possibly named gmapsupp.img although newer software might have another name. It will be an .img file though, and the modification date should give you a clue to which it is. The preloaded topo map should be named gmapprom.img - don't delete that! There is also a time zone map gmaptz.img which shouldn't be deleted. There may be a file named gmapbmap.img too (although not on my 400t).
Before doing anything though, make a backup of your entire Oregon to your computer. It may take awhile because the topo map is almost 3GB, but it could save you a lot of grief in the future.