[Tilecache] metatiles problem

[Markus Spring]

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I have successfully set up tilecache with wms-tiles in Gauss-Krueger coordinates.

When trying to resolve labeling problems by switching meta tiles on, I
consistently run into errors:

An error occurred: Zero length data returned from layer.
~  File "/srv/www/tilecache-2.01/TileCache/Service.py", line 264, in cgiHandler
~    format, image = service.dispatchRequest( params, path_info, req_method, host )
~  File "/srv/www/tilecache-2.01/TileCache/Service.py", line 182, in dispatchRequest
~    return self.renderTile(tile, params.has_key('FORCE'))
~  File "/srv/www/tilecache-2.01/TileCache/Service.py", line 121, in renderTile
~    else: raise Exception("Zero length data returned from layer.")

The URL for this call is (acc. to firebug)

<http://gis.bihk.de:81/tilecache-2.01/tilecache.cgi?REQUEST=getmap&LAYERS=full_background_ohne_cr&PROJECTION=epsg%3A31468&UNITS=m&FORMAT=png&TRANSPARENT=true&SERVICE=WMS&VERSION=1.1.1&STYLES=&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&SRS=epsg%3A31468&BBOX=4558716.249372549,4800321.7506274525,4919960.498745099,5161566.000000002&WIDTH=256&HEIGHT=256>

and the configuration

[full_background_ohne_cr]
type=WMSLayer
url=http://10.215.155.20/wms/background1
layers=l8,l7,l6,l4,l4a,l3,l3a,l2,l1,l0,bgl1,bgl0
extension=png
size=256,256
bbox=4197472,5161566,4681266,5665484
srs=epsg:31468
extent_type=loose
resolutions=1411.110349,705.555175,352.777587,176.388794,88.194397,35.277759,17.638879,8.819440,3.527776,1.763888,0.881944
#### geht das wirklich?
metaTile=true
metaSize=5,5
metaBuffer=10

Whenever I comment out the metaXxx statements, tilecache delivers as expected.

Any hints would be greatly appreciated.

Markus
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