Distracted by a failed MCDU and unfamiliarity with the new STAR procedures at BOS; the flight crew of an E-190 failed to reprogram their FMC for the KRANN arrival to Runway 27 vice 33L as programmed prior to departure. A track deviation resulted which was perceived and corrected by ATC.

Narrative

Approaching Boston Logan cleared to descend via the KRANN1 Arrival to Runway 27. During preflight the FMS had been programmed for the KRANN1 Arrival to Runway 33L. After intercepting the wrong course; ATC advised to turn to a heading and asked which runway we were proceeding to. After landing I was requested to contact the ATC facility by phone. They assured me there was no problem and that; because these RNAV Arrivals are brand new; they were just trying to find out what might have happened because they were new to the controllers also. Enroute we had experienced an MCDU1 failure. It had been written up twice previously; once by me and once by the previous pilot. Each time Maintenance signed it off as 'reset and ops checks O.K.' It must be noted the MCDU on the E-190 is used for both Navigation and Communication. There are no separate radio heads on the aircraft. When one MCDU fails; the other one has to be switched back and forth between navigation and communications input displays. Both cannot be viewed simultaneously. This is a major distraction and increases workload. The flight is very short and there is a very high workload under normal conditions. With one working MCDU; it gets extremely complicated. During our approach briefing we briefed the arrival and landing for the correct runway based on current ATIS; Runway 27. The radios and frequencies were also set for Runway 27 but the FMS (set via the MCDU prior to departure) was still set for the original arrival for Runway 33L and this is where I believe the error occurred. When you review the KRANN1 arrival for this report you will see it is very strange compared to the standard arrivals at most other airports. You have to actually 'backtrack' the routing for the proper runway BEFORE you make the turns and the courses off these turns are very; very close and confusing. This accompanied by a malfunctioning piece of navigation equipment can be troublesome.I'm certain that I could have been more vigilant in assuring that the routing in the FMS was correct. I do also believe that the KRANN1 arrival should be reviewed by ATC for a possible change because it is confusing and I'm certain this is occurring frequently to others who use it.