Roger Waters of Pink Floyd fame spent the last few years performing one of the band's most famous albums, The Wall.  But, he has no plans on reuniting with David Gilmour and the others.  Waters tells The Sun:

"I left Pink Floyd for very good reasons and it was the right and proper thing to do. It was over in 1985 and it’s still over.”

Pink Floyd did perform at Live 8 in 2005.  The lineup included Waters, Gilmour, Nick Mason, and Richard Wright.  Wright passed away in 2006.  

In his conversation with The Sun, Waters mentioned that he was having dinner with Mason.  The problem clearly lies between Waters and Gilmour.