Usually the element not found error is due to having a corrupt file in your My TiVo Recordings folder or a corrupt metadata file in the TiVo Desktop Cache folder. Try moving all your recordings to another folder, if it then starts correctly move a few back at a time until it is broken. The bad file will be in the group you moved last before it broke. Narrow it down to the bad file and delete it. If clearing out the My TiVo recordings folder didn't help, then open the cache folder and delete all the files. TiVo Desktop will simply re-create them the next time it starts (which could take a little while, so don't panic if it is a little slow to start after clearing the cache)
P.S. This question really belongs in the help Forum, not the TiVo Search forum. Hopefully a mod will move it.