Flute playback is not legato.

HI I'm still using 3.6 until 4.0 settles down a bit.
I've just introduced a flute into my music, for the first time, and I notice that on the playback the flute seems to be tonguing every note, which is quite unpleasant.
Slurring the notes seems to make no difference.
Is there a way to achieve a legato sound? I suppose I could use the piano roll editor to extend each note but I'm sure I shouldn't have to do that.