In a puzzling development for a major cable TV operator, Charter Communications (CHTR) - Get Report said Tuesday morning that its chief operating officer is on paid leave.

In a statement issued before the market opened, Charter said Executive Vice President and COO David G. Barford had been replaced "on an interim basis" by CEO Carl Vogel.

The company, controlled by

Microsoft

(MSFT) - Get Report

billionaire Paul Allen, gave no further details. A spokesman for Charter did not return a call requesting comment.

Shares in Charter, already down 90% from their 52-week highs, dropped 36 cents Tuesday morning, or 21%, to $1.39.

Stung by the bankruptcy filing of

Adelphia Communications

(ADELQ)

and industrywide accounting concerns, investors are likely jittery about whatever personal or professional issues may lie behind the Barford announcement.

Over the past year, investors have become increasingly skeptical about the timing and magnitude of cable operators' promises of future cash flows to pay off the billions of dollars they've borrowed to invest in upgraded cable networks.

In August, Charter disclosed that it had received a subpoena from a federal grand jury related to the company's customers and to Charter's policies regarding the capitalization or expense of various costs. Capitalizing costs that should have been expensed is one practice that the now-ousted management of Adelphia is alleged to have done.

At the time Charter made the grand jury disclosure, the company noted that it had recently increased its reserves for uncollected customer accounts receivable, that it had tightened its collection policy and procedures relating to these marginal customers, and that it had disconnected 145,000 "marginal" customers in the first quarter ended March 31.

Tuesday's announcement comes only a day after representatives of Charter and other cable TV operators met with press and analysts in New York to announce a voluntary agreement to disclose

greater and more consistent information about capital expenditures and customer counts.

Barford, who joined Charter in 1995 after working at

Comcast

(CMCSK)

, has been in his current post at Charter for more than two years.