[GRASS-user] Windows r.mapcalc crash

Hi,
I am having trouble running r.mapcalc from my osgeo4w installation in GRASS 7. It quits with the following error:
ERROR: G_calloc: unable to allocate 173*1 bytes of memory at lib/gis/flate.c:319

The region is
Res: 25
Rows: 160
Cols: 160

The grass gis installation is from yesterday. The PC is running W7 64bit and has 8GB memory installed. Any ideas are greatly appreciated.

Thanks,
Frank