This is from Liszt's Hungarian Rhapsody 2 in C# minor. Is this a double sharp sign? It looks kind of funny. The edition is by Julia Rivé-King, a Liszt student.
If you compare your edition with the first edition here http://imslp.org/wiki/Special:ImagefromIndex/67715 you are right, it's a weird sign for a double sharp. I've never seen one like that before.