I've got a bizarre seeming shell issue, with a command in the $PATH that the shell (ksh, running on Linux) appears to cowardly refuse to invoke. Without fully qualifying the command, I get:

#  mycommand
/bin/ksh: mycommand: not found [No such file or directory]

but the file can be found by which:

#  which mycommand
/home/me/admbin/mycommand

I also explicitly see that directory in $PATH:

#  echo $PATH | tr : '\n' | grep adm
/home/me/admbin

The exe at that location seems normal:

#  file /home/me/admbin/mycommand
/home/me/admbin/mycommand: setuid setgid ELF 64-bit LSB executable, x86-64, version 1 (SYSV), for GNU/Linux 2.6.4, dynamically linked (uses shared libs), not stripped

# ls -l mycommand  
-r-sr-s--- 1 me mygroup 97892 2012-04-11 18:01 mycommand

and if I run it explicitly using a fully qualified path:

#  /home/me/admbin/mycommand

I see the expected output. Something is definitely confusing the shell here, but I'm at a loss what it could be?

EDIT: finding what looked like a similar question: Binary won't execute when run with a path. Eg >./program won't work but >program works fine

I also tested for more than one such command in my $PATH, but find only one:

# for i in `echo $PATH | tr : '\n'` ; do test -e $i/mycommand && echo $i/mycommand ; done
/home/me/admbin/mycommand