Read the transcript of the final communications from flight 3407.
No mention of ice being a problem for aircraft. There is a brief incidental mention that there is an area of icing, nut it is clear that nobody sees this as a problem.
No mention of any problems at all.
3407 is there one moment, then gone the next.
Now, look at this line from the transcript.
17:40 - delta 1998: uh negative, delta 1998, we're just in the bottoms and nothing on the TKs
Listening to the tape, it sounds like what the pilot of 1998 said was "... nothing on the TCAS."
TCAS (pronounced T-cass) stands for Traffic Collision Avoidance System, which sends out a lower power non-directional radar pulse and listens for any aircraft transponders in the vicinity. in order to warn pilots of close approaching aircraft. So, what the pilot of Delta 1998 is saying is that at the time ATC asked him to look for a Dash-8 at 2300, 3407's radar transponders had quit working.
One final note. If the Air Traffic Controller is telling the pilot of Delta 1998 to look at 2300 feet altitude for the Dash 8, then that means the last altitude reading returned to the ATC was 2300 feet. Air Traffic radar never received a return showing a loss of altitude, which strongly suggests that the aircraft's entire electrical system quit working while the plane was still half a mile in the air.