I have been using the A2 for a couple of weeks and it has developed numerous problems. I would like to return it to Amazon.es where I bought it from. Although I informed Amazon in my e.mail, regarding returns/exchange etc. that I only wanted to return the A2 for exchange, they say that I must return the complete box that came with the U1 and two mouses. This I do not want to do. I would rather purchase a new A2 or similar. Has any user who purchased from Amazon the U1 complete with standard and A2 mouse had to return just the A2 or did they have to return the complete package. Many thanks.