Permissions problem (Was Newbie getting nowhere)

Trying to make a new start with this question, as it was originally 
about rpmbuild.

When a mail hits my server, postfix generates the following errors:

Oct 19 16:04:10 server local[1324]: fatal: execvp 
/usr/local/tmda-1.1.8/bin/tmda-filter: Permission denied
Oct 19 16:04:11 server postfix/local[1323]: 7B78A14E7A1: 
to=<[email protected]>, relay=local, delay=1, status=bounced (Command 
died with status 1: " /usr/local/tmda-1.1.8/bin/tmda-filter")


The permissions in and around my tmda directory look like this (sorry if 
I've overdone this):

/usr/local
[root@server local]# ls -al
drwxr-xr-x  7  110 screen    4096 Oct 15 07:11 tmda-1.1.8

[root@server tmda-1.1.8]# ls -al
drwxr-xr-x  2  110 screen  4096 Oct 19 16:08 bin

[root@server bin]# ls -al
drwxr-xr-x 2  110 screen  4096 Oct 19 16:08 .
drwxr-xr-x 7  110 screen  4096 Oct 15 07:11 ..
-rw-r--r-- 1  110 screen 58476 Oct 14 06:58 ChangeLog
-rw-r--r-- 1  110 screen  1618 Sep 16 20:41 paths.py
-rw-r--r-- 1 root root     647 Oct 19 15:39 paths.pyc
-rwxr-xr-x 1  110 screen  4601 Oct 13 02:22 tmda-address
-rwxr-xr-x 1  110 screen  3545 Oct 13 03:35 tmda-check-address
-rwxr-xr-x 1  110 screen  3016 Sep 16 20:41 tmda-filter
-rwxr-xr-x 1  110 screen 18375 Oct 14 06:58 tmda-inject
-rwxr-xr-x 1  110 screen  3747 Oct 10 05:19 tmda-keygen
-rwxr-xr-x 1  110 screen 46468 Oct 13 05:38 tmda-ofmipd
-rwxr-xr-x 1  110 screen  9010 Oct 14 23:30 tmda-pending
-rwxr-xr-x 1  110 screen 34894 Oct 14 05:52 tmda-rfilter
-rwxr-xr-x 1  110 screen  2517 Oct 14 06:29 tmda-sendmail

So why the permission denied error?

Just to verify that commands in .forward will work, I tried the 
following in .forward:

"| cat > /home/fred/testcommand"

And the incoming message was indeed piped the testcommand file as expected.

I'm using Fedora Core 5 (which employs SELinux). Any ideas?