As legislators grilled Lt. Gov. Anthony G. Brown on Tuesday over the dismal debut of Maryland's health insurance exchange, the O'Malley administration stood by the website and said it will not switch to the federal version. Rejecting calls to shut down the state's bug-ridden website, Gov. Martin O'Malley's office issued a statement saying the state would keep it running while working to improve it for at least the next 21/2 months. The exchange was created to implement the federal Affordable Care Act and give Marylanders a place to buy health plans or enroll in Medicaid.