Why Charlie Sheen's Plea Deal Went South

6/7/2010 10:30 PM PDT

Why Charlie Sheen's Plea Deal Went South

Sources tell TMZ ... a woman who works in the Pitkin County Jail derailed Charlie Sheen's plea deal today, because she refused to honor the agreement -- even though her own boss signed off on it.

We're told the Pitkin County Sheriff signed off on the deal, as did the undersheriff, the lead prosecutor and Pitkin County District Attorney Marty Beeson.  But the woman who supervises the work release program at the jail threw the monkey wrench before court today, saying she wasn't going to honor the deal because she had problems with the way it was structured.  In short, she would not let Charlie do what all of the parties agreed he could do to complete his 30-day sentence.

We're told the woman made it clear ... she didn't care if her boss made a commitment -- she would not enforce it.  We're told the Sheriff would not force the woman to honor the agreement. 

At that point, attorney Yale Galanter, who brokered the deal for Sheen, pulled the plug.

Charlie is in Aspen tonight but we're told he will not be going back to court tomorrow.

If the parties work it out, a new court date is set for July 12.