Perfectly running python script gives error when run from web.py

I have the following python script which runs perfectly if run separately:

import arcpy 

val = arcpy.GetCellValue_management("D:\dem-merged\lidar_wsg84", "-95.090174910630012 29.973962146120652", "")
print str(val)

I want to expose this as a web service and so I installed web.py and wrote the following code for code.py. but it gives errors(when invoked. compiles fine).

import web
import arcpy        
urls = (
    '/(.*)', 'hello'
)
app = web.application(urls, globals())

class hello:        
    def GET(self, name):

        val = arcpy.GetCellValue_management("D:\dem-merged\lidar_wsg84", "-95.090174910630012 29.973962146120652", "")
        return  str(val)

if __name__ == "__main__":
    app.run()

When i invoke this using http://localhost:8080, i get the following error:

<class 'arcgisscripting.ExecuteError'> at /
ERROR 000582: Error occurred during execution.

Python  C:\Program Files (x86)\ArcGIS\Desktop10.0\arcpy\arcpy\management.py in GetCellValue, line 8460
Web GET http://localhost:8080/
Traceback (innermost first)

C:\Program Files (x开发者_StackOverflow社区86)\ArcGIS\Desktop10.0\arcpy\arcpy\management.py in GetCellValue
          be returned."""
    try:

        retval = convertArcObjectToPythonObject(gp.GetCellValue_management(*gp_fixargs((in_raster, location_point, band_index), True)))
        return retval
    except Exception, e:
        raise e ...
@gptooldoc('GetRasterProperties_management', None)
def GetRasterProperties(in_raster=None, property_type=None):
    """GetRasterProperties_management(in_raster, {property_type})
        Returns the properties of a raster dataset.

I have tried Debugging it in many ways, the code .py runs fine if i just return a "hello". The library i am using is a ArcGIS Geoprocessing toolbox library.

Any ideas as to what might be wrong?

That looks like an error from the third party module. Try finding out what that error code (000582) actually means to the application.