thanks for fixing Robert. This error's gone, but there still seems to be a problem with the dimensions of the ncdf-bricks. If I crop a brick, it returns only one layer, and if i try to rotate it, i get the following error:
>ncp = rotate(nc)
Fehler in dim(res) <- c(ncols, raster@data@nlayers * nrows):
Dimensionen [Produkt 462240] passen nicht zur Länge des Objektes 
which means in english that the dimensions do not fit the object length. As a stack this works without problems..