gstat memory

Hello R-SIG-GEO list,

I know this has come up before but I am having an ongoing memory
problem with the gstat package (gstat out of dynamic memory) that I
can't seem to solve.

I am using R to interpolate DEMs from LiDAR xyz point files and mosaic
them together via RSAGA.  The script uses a loop to load in each xyz
point file, and interpolate over a regular lattice of points using idw
from gstat.  Although large, the computational requirements within
each iteration of the loop should be well within my system's ability
so it seems like it is a cumulative effect (note I can restart the
process at the last loop that triggered the error and the iteration is
successful).  I am removing temp objects and running gc() at the end
of every loop.

It proceeds normally for about 5-10 iterations and physical memory use
on my system (VISTA 64 bit, 12GB RAM) gradually increases over time
until I get the "gstat out of memory" error. Here is the relevant
portion of the loop:

...

  path<-"E:/LidarData/1_Ground_First_Return/UTM17/"
  filen<-paste(path, centre_tile$TILECODE, ".xyz", sep="")
  xyzi<-read.table(filen, sep=",", header=F)
  names(xyzi)<-c("x","y","z","i")

  for(j in 1:length(tile_group_names)){
      filen<-paste(path, tile_group_names[j], ".xyz", sep="")
      tmp_xyzi<-read.table(filen, sep=",", header=F)
      names(tmp_xyzi)<-c("x","y","z","i")
      xyzi<-rbind(xyzi,tmp_xyzi)

  }
      coordinates(xyzi)=~x+y
  # note grid_coords is just the regular lattice that is created from
the current tile coordinates
  coordinates(grid_coords)=~x+y

  # do the interpolation
  interp<-idw(z~1, xyzi, grid_coords, nmax=4,maxdist=2, idp=1.0)

  names(interp)<-c("z","var")
  slot(interp,"data")<-data.frame(slot(interp,"data"))
  finalSPntsDF<-SpatialPointsDataFrame(interp, data.frame(interp$z),
              proj4string = CRS(as.character(NA)), match.ID = TRUE)


  finalSPDF<-SpatialPixelsDataFrame(finalSPntsDF,
data.frame(interp$z), tolerance = sqrt(.Machine$double.eps),
    proj4string = CRS(as.character(NA)))

... On a related note - I have tried using the 64 bit version of
Revolution but unfortunately the gstat package has not been ported. 
Has anyone contemplated or begun a 64 bit port of this package?

Thanks

Murray