Green Screen question

Keying some recent green screen footage. The greens were not lit as well as they could of been but still not bad results. I'm using dvGarage DV Matte to do the keying. I'm getting on well but one of the problems I'm having on one of the clips is that after I use screen fix to get the key as good as it can be and then putting on Matte pro plugin. I'm finding traces of white lines around the talent. After the initial key and tweaking the black & white points then adjusting the high & low points I get a quite convincing key. Then playing through the footage I see short white lines around the edges of the talent can't seem to get rid of them. I have tried adjusting the V & H blur controls but if I go to far on the setting then I see the white lines. I'm also seeing jagged edges around the talent. I am using 1920x1080i footage in FCP6. Any pointers to getting this better?
Thanks