The Chesapeake and Potomac Telephone Co. of Maryland this afternoon was scrambling to find the cause of a widespread problem that was preventing the connection of some telephone calls in Maryland, Washington and Virginia.

People were getting fast busy signals or recordings when the connection couldn't be made, said Ralph G. Blunt, a C&P; spokesman. The intermittent problem first became evident at 11:40 a.m. today. The problem seemed to involve the company's switching stations, which relay calls from one group of telephone exchanges to another.