Problem
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I run the dbx in csh as follows
% dbx mainprog
-- The following is the systemm replay
Type 'help' for help.
reading symbolic information ...warning: stab entry unrecognized: name ,type 45, class a8, value 0'
You might want to enter "nested depth underflow" into the search box at the IBM site. It would get you 49 hits where the first one is addressing the problem in AIX 4.3.3 (clearly not suiting you) and the second one is about AIX 5.1 - BINGO!