Guidant Corp. warned doctors Thursday of more problems with some of its pacemakers, saying at least 10 people have been hospitalized because of flaws in some essential functions. The alert involves Guidant’s Insignia and Nexus lines of pacemakers. The NY Times reported that Senator Charles Grassley, chairman of the Senate Finance Committee, notified Guidant that his committee is investigating where the company had violated a 2003 agreement that required it to notify the government of product problems. The FDA considers the pacemaker action to be a recall, making it the 5th recall by the company. The latest problems include intermittent or permanent loss of pacing output, loss of telemetry, and the appearance of a warning message when the device is being checked, a spokesman for Guidant said.