Sonus

(SONS)

got slammed late Monday after warning of yet another shortfall.

The Chelmsford, Mass.-based Internet phone switch maker says preliminary numbers for the first quarter ended March 31 show a net loss on sales of about $32 million. Analysts had been looking for a penny profit on $41 million in revenue, according to Reuters Research.

Sonus, which

warned last month of a lower-than-expected sales total for the fourth quarter ended in December, says it does not expect to complete an ongoing accounting review "until early May."

"We are disappointed that our revenue is lower than anticipated. The revenue shortfall is due to schedule delays for the conversion of certain shipments to revenue and the late renewals of several annual maintenance contracts," CEO Hassan Ahmed said in a press release Monday.

The company hit a bookkeeping snag last year and is currently working with auditors to clean up its records.

Sonus shares fell 80 cents, or 21%, to $2.93 in after-hours trading.