[Tilecache] MetaTile causes "Exception: Zero length data returned from layer."

[Mak Kolybabi]

Whenever I enable MetaTile in TileCache, I cannot seed the cache. If I turn it off, it
works perfectly.

The error message I receive is:
% /var/www/tilecache/tilecache_seed.py -f --bbox=133977.89,5427363.5,766071.31,6661918.0 base 0 5
###### (0, 17, 0), (2, 21, 0)
Traceback (most recent call last):
  File "/var/www/tilecache/tilecache_seed.py", line 9, in <module>
    TileCache.Client.main()
  File "/var/www/tilecache/TileCache/Client.py", line 162, in main
    seed(svc, layer, map(int, args[1:3]), bboxlist , padding=options.padding, force = options.force, reverse = options.reverse)
  File "/var/www/tilecache/TileCache/Client.py", line 117, in seed
    svc.renderTile(tile,force=force)
  File "/var/www/tilecache/TileCache/Service.py", line 140, in renderTile
    else: raise Exception("Zero length data returned from layer.")
Exception: Zero length data returned from layer.

When I disable MetaTile, it works as expected:
% /var/www/tilecache/tilecache_seed.py -f --bbox=133977.89,5427363.5,766071.31,6661918.0 base 0 5
###### (0, 17, 0), (2, 21, 0)
Cache miss: -180.0,5370278.0,315724.0,5686182.0, Tile: x: 0, y: 17, z: 0, time: 1.78748202324
00 (000000, 000017) = (-180.0000 5370278.0000 315724.0000 5686182.0000) [1.7885s : 0.559/s] 1/8
...

My TileCache config is as follows:
% cat /etc/tilecache.cfg
[cache]
type            = Disk
base            = /var/db/tilecache

[base]
type            = MapnikLayer
mapfile         = /var/www/layers/base.lay
extension       = png
resolutions     = 1234, 617, 308, 154, 77
metaTile        = true

[segments]
type            = MapnikLayer
mapfile         = /var/www/layers/segments.lay
extension       = png
resolutions     = 1234, 617, 308, 154, 77
metaTile        = true

I've been banging my head against this bug for a couple of hours. I've searched this
mailing list's archives, as well as Google, and though many other users seem to have
encountered the problem I'm experiencing, I've not seen any solutions.

Any help you could offer would be very much appreciated.

--
Mak Kolybabi
Programmer
Telenium Inc.
204-957-2821
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