[Tilecache] Trouble with tilecache config

[Tom Farnham]

I'm attempting to setup tilecache for use with my postgis db and  
mapserver. I'm running Mac OS X.

I get the following when attempting to view a tile:

An error occurred: 'Water'
   File "/Library/WebServer/CGI-Executables/TileCache/Service.py",  
line 479, in cgiHandler
     format, image = service.dispatchRequest( params, path_info,  
req_method, host )
   File "/Library/WebServer/CGI-Executables/TileCache/Service.py",  
line 395, in dispatchRequest
     tile = WMS(self).parse(params, path_info, host)
   File "/Library/WebServer/CGI-Executables/TileCache/Service.py",  
line 120, in parse
     return self.getMap(param)
   File "/Library/WebServer/CGI-Executables/TileCache/Service.py",  
line 124, in getMap
     layer = self.service.layers[param["layers"]]

Any help would be appreciated

tom