argument is null

[antonio de la peña]

I get an "Argument is null" message in Studio everytime I try to create or
edit a layer. The message comes accompanied by this in the place where the
preview should appear (using the ajax viewer, but I get a similar trace with
DWF Viewer):

Resource was not found:
Session:f81a5c02-ffff-ffff-8000-0016362153b1_en//MapDefinition41.MapDefiniti
on
Resource was not found:
Session:f81a5c02-ffff-ffff-8000-0016362153b1_en//MapDefinition41.MapDefiniti
on Exception occurred in method MgResourceDefinitionManager.GetDocument at
line 483 in file
c:\build_tux_area\mgdev\server\src\services\resource\ResourceDefinitionManag
er.cpp 

This also happens with the Sheboygan sample and on the load procedure
screen, when the Save resources: Layers checkbox is selected.

This seems like the same issue.
https://mapguide.osgeo.org/servlets/ReadMsg?listName=users&msgNo=162

I can't move on! Thanks for your help.

Antonio de la Peña Jiménez