You have to store the original selection first.
Here's a script that I made to cut selected facets from a uv map. Theirs a final version on my powerbook -with some lines that checks the selection first before executing and declared variables- but I don't have it with me right now.
If the script doesn't help you... check the following
polySelectBorderShell 1; // selects uv border
polySelectBorderShell 0; // selects uv shell
Cheers!Rudy Massar
global proc cutFaceFromUvMap(){
// store the selected faces
$selFaces = ls -sl -flatten
;
// define the border of the selection and cut the UV's
$faceToEdge = polyListComponentConversion -toEdge -border
;
polyMapCut -name "FaceFromUvMap" $faceToEdge;
// select the original faces
select $selFaces;
// makes a conversion list from selected components
$makeFaceMove = polyListComponentConversion -toUV
;
// select the converted components
select $makeFaceMove;
};