Do you have a backup? If so, you could reformat the unit and copy over the backup.
If not, when it is connected to your computer, are files and folders visible on the unit when using Windows explorer? If so, make a backup with windows explorer, as while it may have a corrupted application, you want ot be sure you safely backup other items - especially the map folder.
Then start up TomTom home and see if you can "delete from Unit" the application - which sounds like it is corrupted.
Then, disconnect it from Home, and run the clear_flash tool. Reconnect it to home after it flashes and boots back up, and go to "Updare My device" It should reload a new clean application on the unit.
If it all comes back up after you disconnect it from home and your computer, you are good to go. Make a new backup.
If not - note that what you need at a minimum to get back up and running is the map folder. If you have that, you could reformat the uinit, then have Home install the application, and then copy over the map folder.
If you have other items like custom POI's - you could work on moving them over after you unit is running OK.
