Well at least on the 04+ I have seen a lot of questions about why their remotes aren't working. This is pretty easy to check and fix should it be your issue. The problem I have seen on a few and on both of my remotes is that the battery clip comes out of its connections, thus losing power. You need a soldering iron, solder, and about 2 minutes to fix this. Open your remote with a knife and look at the battery clips. Try wiggling it and pulling (very lightly) to see if it comes out at all. If it does then you know you need to re-solder the connections. Things are small so I found it easiest to melt the solder onto the iron and then just touch it to the connections to apply it.
Now there are two connections to solder seen here:
and here
Let it cool for a minute then reassemble and try it out.
