LCD 4 Line 40 Character Interfacing

I am trying to get a 4 Line 40 Character LCD Display to display characters but so far have been unable to do so. I have a couple of 2 Line 24 Character displays that I have working but I can't get the 4 line display to display any characters. I have read what little information I have been able to find but it has been of little help. The 4 Line uses 2 of the same controllers that the 2 line display uses ( all lines are common except for the Enable lines. I have set it up on the bench with jumpers and switches. Has anyoneinterfaced to a 4 Line display ??

In my experiment, when the driver chips is same - e.g. HD44780 - i can change the modules without problem.

40 characters in 4 lines , thats 10 char's per line.
I can't find any lcd's like that - i dont think such a HD44780 lcd exists

are you sure it is a HD44780 based lcd?

40 Character 4 line means 40 characters per line and total = 40*4 = 160 characters.

This is same as you describe 16 char. x 2 line LCD. It has 2 lines with 16 characters each.

ok, thanks for clearing that up

LCD's with more then 80 characters use a diffirent pinout then the ones with less then 80 and have 2 enable signals
One enable for the first controller - line 1 & 2
and another for the controller for lines 3 & 4

see http://home.iae.nl/users/pouweha/lcd/lcd.shtml section 2.1

Thanks to all that posted replys. My problem was that I did not have the correct connector pin out. For what is worth 4 Line x 40 Character displays have a 16 pin connector layed out as follows:
PIN # 1 DB7
PIN #2 DB6
PIN #3 DB5
PIN #4 DB4
PIN#5 DB3
PIN#6 DB2
PIN#7 DB1
PIN#8 DB0
PIN#9 Enable #1
PIN#10 R/W
PIN#11 RS
PIN#12 LCD Drive
PIN#13 5 VDC Ground
PIN#14 5 VDC Positive
PIN#15 Enable #2
PIN#16 No Connection

Tne same instruction set that applies to the 2 line displays applies to each of the 2 40 Character sets ... That is all the control/data lines are paralleled except for the Enable Lines so Enable #1 controls Display Lines 1 & 2 of the 4 Line Display and Enable #2 controls Display Lines 3 & 4. The Instructions/Data is applied to the display when the Enable Line goes from a HIGH to a LOW. The Instruction/Data needs to be on the PINs and stable when this occurs.
I am interfacing a 4 Line x 40 Character display with a PIC18F452 ( a flash Microcontroller ) and a 12 Keyboard and both are now working ( it took me most of last night to figure out the proper PIN Out for the LCD Display ) from that point on it was a snap