gdal - gdalwarp won't export AAIGrid

I'm trying to use gdalwarp to reproject an ascii grid file. According to http://www.gdal.org/formats_list.html this shouldn't be a problem and indeed I can happily use gdal_translate to create grd files (AAIGrid) but not gdalwarp:

gdaltest 14:40:08 $ gdal_translate -of AAIGrid rj_DEM_1978.grd junk.grd
Input file size is 401, 301
0...10...20...30...40...50...60...70...80...90...100 - done.
gdaltest 14:40:25 $ rm junk.*
gdaltest 14:40:41 $ gdalwarp -of AAIGrid rj_DEM_1978.grd junk.grd

Output driver `AAIGrid' not recognised or does not support
direct output file creation.  The following format drivers are configured
and support direct output:
  VRT: Virtual Raster
  GTiff: GeoTIFF
  NITF: National Imagery Transmission Format
  HFA: Erdas Imagine Images (.img)
  ELAS: ELAS
  MEM: In Memory Raster
  FITS: Flexible Image Transport System

  BMP: MS Windows Device Independent Bitmap
  PCIDSK: PCIDSK Database File
  ILWIS: ILWIS Raster Map
  SGI: SGI Image File Format 1.0
  Leveller: Leveller heightfield
  Terragen: Terragen heightfield
  netCDF: Network Common Data Format
  HDF4Image: HDF4 Dataset
  ISIS2: USGS Astrogeology ISIS cube (Version 2)
  ERS: ERMapper .ers Labelled

  RMF: Raster Matrix Format
  RST: Idrisi Raster A.1
  INGR: Intergraph Raster
  GSBG: Golden Software Binary Grid (.grd)
  GS7BG: Golden Software 7 Binary Grid (.grd)
  PNM: Portable Pixmap Format (netpbm)
  ENVI: ENVI .hdr Labelled
  EHdr: ESRI .hdr Labelled
  PAux: PCI .aux Labelled
  MFF: Vexcel MFF Raster

  MFF2: Vexcel MFF2 (HKV) Raster
  BT: VTP .bt (Binary Terrain) 1.3 Format
  LAN: Erdas .LAN/.GIS
  IDA: Image Data and Analysis
  GTX: NOAA Vertical Datum .GTX
  NTv2: NTv2 Datum Grid Shift
  CTable2: CTable2 Datum Grid Shift
  ADRG: ARC Digitized Raster Graphics
  SAGA: SAGA GIS Binary Grid (.sdat)


gdaltest 14:40:52 $ which gdal_translate
/Library/Frameworks/GDAL.framework/Programs/gdal_translate
gdaltest 14:41:05 $ which gdalwarp
/Library/Frameworks/GDAL.framework/Programs/gdalwarp
gdaltest 14:41:10 $ 

As you can see, the format list is somewhat shorter than normal. From the two which commands at the bottom you can also see that both gdalwarpand gdal_translateare located in the same library. Does anyone have an explanation for this? I can work around it easily enough but this shouldn't be happening, should it?