Create table in functions

Hello,

I striped down my function up to a strange thing:

web=# create function pHelpTable( )
web-# returns int
web-# As '
web'# Begin
web'# Create Table Temp_NumTable ( Num int ) ;
web'#
web'# return 17 ;
web'# End; '
web-# language 'plpgsql' ;
CREATE
web=#
web=# select pHelpTable( );
ERROR: copyObject: don't know how to copy 611
web=#

What does this mean? The ERROR is caused by the Create Table statement
(when I removed it from my complex function it worked well).
So why doesn't this work and what copy function fails here??

Kind regards

Andreas.