Mos Def seemed all set to take on a starring role in a new HBO series 'Enlightened,' but now reports are indicating that the rapper/actor failed to reach a deal with the network before filming began on the series last week in Los Angeles. In turn, Mos has been replaced by Timm Sharp -- star of the short-lived cult T.V. series 'Undeclared.'

The show centers around a character named Amy -- played by 'Jurassic Park' actress Laura Dern. According to HBO, Dern's subject has lived a rough life with many bad influences, habits and decisions but has a spiritual awakening, becomes enlightened and then all sorts of trouble ensues when her destructive relationships with friends and family are further altered by her new mindset.

Mos Def's role was to be Dern's boss in the series, but now Sharp will take over those responsibilities. The show, which is written and directed by 'School of Rock' author Mike White, also features Luke Wilson as Dern's drug-addled ex-husband. The series seems poised to be a comedy with equal doses of grit, wit and drama.

While we were definitely excited for the prospect of Mos Def getting a great role on a television series, this should free up some of his time to keep working on music. There's been no word on a follow-up to 2009's excellent 'The Ecstatic,' but fans are hoping the wait won't be too long this time around.