Stored procedure array limits

I have a large stored procedure with 16 arrays, mostly varchar, each
with dimension 3000.  The procedure works fine on a small number of rows
used from these arrays but gets the following error for large rowsets:

  ERROR:  invalid array subscripts
  CONTEXT:  PL/pgSQL function "name_search" line 64 at assignment

I have not exceeded the size of the arrays, index-wise.

I increased max_stack_depth to 32768 and work_mem to 32768 but without
effect.

If I comment out two particular arrays (that can have null values), it
also runs OK.

Anybody have any ideas?

Paul