Steps followed:

1.) Installed 5.1.22

2.) Create table trackviews 

CREATE TABLE `trackviews` (
`clientID` int(11) NOT NULL DEFAULT '0',
`fromClientID` int(11) NOT NULL DEFAULT '0',
`trackDate` int(11) NOT NULL DEFAULT '0',
`data` int(11) NOT NULL DEFAULT '0',
PRIMARY KEY (`clientID`,`fromClientID`),
KEY `trackDate` (`trackDate`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

3.) Create table mym

CREATE TABLE `mym` (
`clientID` int(11) NOT NULL DEFAULT '0',
`realname` char(15) DEFAULT NULL,
PRIMARY KEY (`clientID`)
) ENGINE=innoDB DEFAULT CHARSET=latin1; 

4.) Inserted rows in both the tables with above data.


4a.) mysql> select * from trackviews;
+----------+--------------+------------+--------+
| clientID | fromClientID | trackDate  | data   |
+----------+--------------+------------+--------+
|       32 |       394466 | 1202929904 | 999905 | 
|       32 |       395218 | 1202549293 | 999904 | 
|       32 |       395891 | 1202525736 | 999903 | 
|       32 |       396069 | 1202669189 | 999902 | 
|       32 |       396326 | 1202945744 | 999901 | 
+----------+--------------+------------+--------+
5 rows in set (0.00 sec)

4b.) mysql> select * from mym;
+----------+--------------+
| clientID | realname     |
+----------+--------------+
|   394466 | LaurenAndNic | 
|   395218 | sop          | 
|   395891 | da           | 
|   396069 | t            | 
|   396326 | stepha       | 
+----------+--------------+
5 rows in set (0.00 sec)

   
5.) Run the following queries on 5.1.22

5a.) Ran the following on 5.1.22
================================

5b.)   mysql> select tv.fromClientID as ClientID, tv.trackDate,p.realname  
from trackviews tv left join mym p on (tv.fromClientID=p.clientID) 
where tv.clientID=32 order by trackdate ASC limit 5;

+----------+------------+--------------+
| ClientID | trackDate  | realname     |
+----------+------------+--------------+
|   395891 | 1202525736 | da           |
|   395218 | 1202549293 | sop          |
|   396069 | 1202669189 | t            |
|   394466 | 1202929904 | LaurenAndNic |
|   396326 | 1202945744 | stepha       |
+----------+------------+--------------+
5 rows in set (0.01 sec)


RESULT OK


5c.)  mysql> select tv.fromClientID as ClientID, tv.trackDate,p.realname  
from trackviews tv left join mym p on (tv.fromClientID=p.clientID) 
where tv.clientID=32 order by trackdate DESC limit 5;

+----------+------------+--------------+
| ClientID | trackDate  | realname     |
+----------+------------+--------------+
|   396326 | 1202945744 | stepha       |
|   394466 | 1202929904 | LaurenAndNic |
|   396069 | 1202669189 | t            |
|   395218 | 1202549293 | sop          |
|   395891 | 1202525736 | da           |
+----------+------------+--------------+
5 rows in set (0.00 sec)


RESULT OK


6.) Installed 5.1.23-rc

6a.) Ran the following On 5.1.23-rc
===================================

6b.)  mysql> select tv.fromClientID as ClientID, tv.trackDate,p.realname 
    from trackviews tv left join mym p on (tv.fromClientID=p.clientID)
    where tv.clientID=32 order by trackdate ASC LIMIT 5;
+----------+------------+--------------+
| ClientID | trackDate  | realname     |
+----------+------------+--------------+
|   395891 | 1202525736 | da           | 
|   395218 | 1202549293 | sop          | 
|   396069 | 1202669189 | t            | 
|   394466 | 1202929904 | LaurenAndNic | 
|   396326 | 1202945744 | stepha       | 
+----------+------------+--------------+
5 rows in set (0.00 sec)

RESULT OK


6c.) mysql> select tv.fromClientID as ClientID, tv.trackDate,p.realname 
from trackviews tv left join mym p on (tv.fromClientID=p.clientID)
and tv.clientID=32 order by trackdate DESC LIMIT 5;
+----------+------------+--------------+
| ClientID | trackDate  | realname     |
+----------+------------+--------------+
|   396326 | 1202945744 | stepha       | 
|   396069 | 1202669189 | t            | 
|   395891 | 1202525736 | da           | 
|   395218 | 1202549293 | sop          | 
|   394466 | 1202929904 | LaurenAndNic | 
+----------+------------+--------------+
5 rows in set (0.00 sec)


RESULT NOT OK.


6d.)  mysql>select tv.fromClientID as ClientID, tv.trackDate,p.realname 
from trackviews tv left join mym p on (tv.fromClientID=p.clientID)
order by trackdate DESC LIMIT 5;

+----------+------------+--------------+
| ClientID | trackDate  | realname     |
+----------+------------+--------------+
|   396326 | 1202945744 | stepha       |
|   394466 | 1202929904 | LaurenAndNic |
|   396069 | 1202669189 | t            |
|   395218 | 1202549293 | sop          |
|   395891 | 1202525736 | da           |
+----------+------------+--------------+
5 rows in set (0.00 sec)

RESULT OK


6e.) mysql> select tv.fromClientID as ClientID, tv.trackDate,p.realname
from trackviews tv, mym p where tv.fromClientID=p.ClientID
and tv.clientID=32 order by trackdate DESC limit 5;

+----------+------------+--------------+
| ClientID | trackDate  | realname     |
+----------+------------+--------------+
|   396326 | 1202945744 | stepha       | 
|   396069 | 1202669189 | t            | 
|   395891 | 1202525736 | da           | 
|   395218 | 1202549293 | sop          | 
|   394466 | 1202929904 | LaurenAndNic | 
+----------+------------+--------------+
5 rows in set (0.00 sec)

RESULT NOT OK

6f.) mysql>select tv.fromClientID as ClientID, tv.trackDate,p.realname
from trackviews tv, mym p where tv.fromClientID=p.ClientID
order by trackdate DESC limit 5;

+----------+------------+--------------+
| ClientID | trackDate  | realname     |
+----------+------------+--------------+
|   396326 | 1202945744 | stepha       |
|   394466 | 1202929904 | LaurenAndNic |
|   396069 | 1202669189 | t            |
|   395218 | 1202549293 | sop          |
|   395891 | 1202525736 | da           |
+----------+------------+--------------+
5 rows in set (0.00 sec)

RESULT OK