It's the socket that holds the turn signal light bulb in. There is a metal strip that gets brittle on older Crossfires and doesn't make connection anymore. It is usually enough to pull the strip out slightly so it makes connection again but on mine, when I did that it just fell apart.
I'm sure it could be fixed with a soldering iron but I don't have one and so I went looking on ebay. There are several vendors who sell Xfire parts and most of them did not want to sell me the socket seperately as it is part of the light assembly. Finally found one who is good and I got some parts from in the past. He charged me $10 for the sockets + bulb. Interestingly, his comes from a 2007 Xfire and the socket looks more solid!
Glad I found him as from what I read on the forum these parts are very hard to find since they aren't made anymore.