Hi! I've had the same problem with this tool. It seems to be a bug concerning the naming of the input raster file. Suppose the input raster is named "c:\folder1\folder2\img.tif". The source code will isolate "img.tif" as the name of the "InRas" field of the dasymetric table. However, when the table is actually created, the field is named using only the file's base name, not the extension as well. So, it will be named "img". Portion ".tif" of the string must be removed. I have come up with this solution:
Replace the following code line of "dasy.py":
InRasField = (InRas.split("\\" ))[-1]
with:
InRasField = (InRas.split("\\" ))[-1]
theRCharOffset = (-1) * len(".tif")
InRasField = InRasField[:theRCharOffset]
You'll find it in the first 30 lines of the python source code. Also, try giving a short name to your input raster (up to 10 chars). This worked for me, I hope it works for you too!