Probably a little late to help, however, in case its of assist to others. The errors likely a result of the Ascii file when created not being assigned or converting the null values to the desired number. If you open the Acssi file for example in notepad, you'll see the values "-1.#IND" listed throughout. In my situation, the value of "-1.#IND" occurred when nodata values were assigned a non-numeric value (i.e. nan). This appears to result from running different geoprocesses in QGIS for example, of when doing raster calculations where values are divided by 0.
You need to ensure that your nodata values are transformed correctly (check the Ascii itself, rather than just the metadata of the file). In QGIS I use gdal_warp to ensure null values reflect the desired number (i.e. -9999).