Super slow query with ORDER by killing me!

sage advice requested please!

[data_conv]

Hello and thank you kindly for taking a look at this with me.
Your time is greatly appreciated. I am having a great deal of trouble with a query that is running super slow. Details follow:
Just the facts:
1)I wrote a php pagination function to which I pass a query that generates about 5500 results and displays it in pages of 25.

2) Showing rows 0 - 25 (5,500 total, Query <b>took 23.4910 sec</b>)

3) When I remove the ORDER BY the query takes less than one second.

4) I am using ORDER BY a datetime field to enable me to display results by the most recently accesed record(to the second). I need to maintain this feature.

5) Indexed, the datetime field contains the same number as the records returned.

Comments:
I am using InnoDB.
As the query results are displayed in pages - each new page takes roughly the same amount of time to load.
I am ok at php/mysql but not great (obviously).

The query: (names have been changed to protect the guilty)
SELECT t1.field, t1.field2, t2.field,
t1.field3, t1.field4, t3.field,
CONCAT(t4.field1,' ', t4.field2) AS somename,
t1.field5, t5.field, t6.field, t2.field2,
t2.field3, t7.field, t1.field6
FROM table1 AS t1
LEFT JOIN table2 AS t2 ON t1.field=t2.field
LEFT JOIN table3 AS t3 ON t1.field2=t3.field
LEFT JOIN table4 AS t4 ON t1.field3_id=t4.field
LEFT JOIN table5 AS t5 ON t1.field4_id=t5.field
LEFT JOIN table6 AS t6 ON t1.field5_id=t6.field
LEFT JOIN table7 AS t7 ON t1.field6=t7.field
ORDER BY t2.field2 DESC

[Demaestro]

I am not familiar with that DB but try running an explain

explain SELECT t1.field, t1.field2, t2.field,
t1.field3, t1.field4, t3.field,
CONCAT(t4.field1,' ', t4.field2) AS somename,
t1.field5, t5.field, t6.field, t2.field2,
t2.field3, t7.field, t1.field6
FROM table1 AS t1
LEFT JOIN table2 AS t2 ON t1.field=t2.field
LEFT JOIN table3 AS t3 ON t1.field2=t3.field
LEFT JOIN table4 AS t4 ON t1.field3_id=t4.field
LEFT JOIN table5 AS t5 ON t1.field4_id=t5.field
LEFT JOIN table6 AS t6 ON t1.field5_id=t6.field
LEFT JOIN table7 AS t7 ON t1.field6=t7.field
ORDER BY t2.field2 DESC

Post what is outputs

[data_conv]

Hi Thanks, this is in MySQL in case I didn't mention it.

1 SIMPLE t1 ALL NULL NULL NULL NULL 6012 Using temporary; Using filesort
1 SIMPLE t2 ALL NULL NULL NULL NULL 6012
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 1 t3.table3 1
1 SIMPLE t4 eq_ref PRIMARY PRIMARY 4 t4.table4 1
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 1 t5.table5 1
1 SIMPLE t6 eq_ref PRIMARY PRIMARY 1 t6.table6 1
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 1 t7.table7 1