I have cleaned up my python module tree (it was a mess), reconfigured both numarray and Numeric and it's now working well. It seems I had troubles with different versions of Numeric. Perhaps python-tables uses a function that I don't in the NumPy packages, because all was working well since no calls were made to python-tables.
Anyway, congratulations for this package that is really handy to use and so efficient. Jean-Philippe
