memory leaking [nskeyedunarchiver decodeobjectforkey]

every i slight nsmutabledata leaking i can't figure out block it. thedata's keep count upped after decoder allocated initialized i have thought why. i am stranded keep count 2 during finish slight attempting redeem causes an app crash.

- (void)readvenuearchivefile:(nsstring *)infile key:(nsstring *)inkey
{
    nsmutabledata *thedata;
    nskeyedunarchiver *decoder;


    thedata = [nsdata datawithcontentsoffile:infile];

    decoder = [[nskeyedunarchiver alloc] initforreadingwithdata:thedata];

    venueiolist = [[decoder decodeobjectforkey:inkey] mutablecopy];

    [decoder finishdecoding];

    [decoder release];
}