Dan Rather accused CBS executives yesterday of not having "lived up to their obligation to allow me to do substantive work there" as the network announced his departure after a 44-year career. CBS officials heaped praise on the longtime anchor, even as they were ushering him out the door yesterday. Rather, for his part, made clear his frustration with the network for refusing to renew his contract or give him an ample workload at "60 Minutes." --Snip-- Rather, who anchored the "CBS Evening News" for 24 years, relinquished the post early last year after apologizing for a 2004 story --...