False mysql query results

I've run into a problem that is quite frankly baffling the heck out of me.

I'm using PHP 4.3.4 / MySQL 4.0.14 / Redhat 8.3 and PHP 4.3.4 / MySQL 4.0.16 / Redhat 8.3.

I have a database where I am performing some cleanup and I do the following:
1. Get and make a list of the current subjects a student is enrolled in.
2. Delete that list of subjects so the student isn't enrolled in anything at all.
3. Loop through the list of classes from #1, and...
a. Get the appropriate class the student *should* be enrolled in (based on his location and career)
b. Insert that information.
c. Check to make sure that information was inserted, and if it wasn't, then repeat the Insert.
d. If the information was inserted in 3.b. or the second attempt in 3.c, then insert in another table information associated with a related enrollment in a forum.
e. Perform similar checks as in 3.a. - 3.c. above.
f. Get the next class and repeat 3.a. - 3.e.

The mysql_query is handled by the following function:

function qAlumnos2($q, &$numRows, &$affRows) {
global $link2, $debug;

$numRows = $affRows = -1;
$r = mysql_query($q, $link2);
$which = strtoupper(substr($q, 0, 6));
if ($which == "INSERT" || $which == "UPDATE" || $which == "DELETE")
$affRows = @mysql_affected_rows($link2);
else
$numRows = @mysql_num_rows($r);
if ($debug) echo "qAlumnos2 AFFECTED_ROWS: $affRows, numRows: $numRows, q: $q<hr>\n";
return $r;
}

Here's the problem:
Half the time, the results I am getting from the affected_rows and num_rows are false
.
For example:
The first pass of inserting a student and his info:

qAlumnos2 AFFECTED_ROWS: 1, numRows: -1, q: INSERT INTO alumnos.inscripcion_net (alcodigo, macodigo, mmcodigo, infecha, ininscripto) VALUES (8860, 10, 1, '2004-03-24 18:22:30', '1')

Notice that "AFFECTED_ROWS" is returning a 1. That's a lie, nothing was inserted.

Now (since I don't trust my insertion) I check to see if the info was actually inserted:

qAlumnos2 AFFECTED_ROWS: -1, numRows: 1, q: SELECT macodigo FROM alumnos.inscripcion_net WHERE alcodigo = 8860 AND macodigo = 10

Notice that "numRows" is returning a 1. That's a lie too, nothing actually was Inserted after all.

The "qAlumnos2" function must be screwing things up you must be thinking... but it actually does what it should half the time (so it does work), and I'm using it elsewhere without problems. For example, when I delete the student's existing classes 1 by 1 (not efficient, but I'm performing other deletions related to each class).

So... I tried:

1. Establishing a separate $link variable when I connect to the database. It did not make a difference.
2. Eliminating the "qAlumnos2" function and using $r = mysql_query("SQL QUERY HERE...", $link2);
along with mysql_num_rows($r) and mysql_affected_rows($link2)
and I still had the same problems.

So, I'm basically lost at this point.

If anybody has suggestions, please toss them my way. I've got 10,000+ students I need to process ASAP, but if I process them now, basically all of them will be missing at least 1 or more classes.-

Thanks in advance,

Christopher D. Vrooman