bad interpreter: Permission denied

So I'm doing the Symantec live update installation on the servers, and they all work - except one.  The only one I really care about, our main server.

It goes about halfway through the install script, and then dies:

[root@dg tmp]# /opt/Symantec/symantec_antivirus/sav liveupdate -u
Command failed: Problem with LiveUpdate.
Check that java directory is in PATH
Unable to perform update 

Crud.

The log's pretty good, though, and it showed which file it failed on:

16-Feb-10 10:24:58 AM Making /tmp/1266333784179/1266333839866/navuphub.dis executable ...
16-Feb-10 10:24:58 AM Running /tmp/1266333784179/1266333839866/navuphub.dis ...
16-Feb-10 10:24:58 AM Error running /tmp/1266333784179/1266333839866/navuphub.dis with reason: java.io.IOException: java.io.IOException: Permission denied. 

Huh?  Permission denied?  I'm running as root! I trace the file down in /tmp, and try to execute it.  The top line says

#!/bin/sh
like it should, so there shouldn't be any problem:

[root@dg 1266333839866]# ./navuphub.dis
-bash: ./navuphub.dis: /bin/sh: bad interpreter: Permission denied

Uh-oh.  So I try executing /bin/sh - it works.  I unlink and link back to it - it's a symbolic link to bash in RHEL.  It still works.  Now I'm getting nervous.

I copy that little .dis file over to ~, and... the file executes.

I slap myself upside the head.  I do a mount -l, and sure enough:

/dev/hda5 on /tmp type ext3 (rw,nodev,noexec) [/tmp]

In a fit of paranoia a few years ago, I made /tmp unable to execute programs.  That's what that 'noexec' parameter in /etc/fstab does - no programs, no scripts. A remount of temp fixed it.