I have the same monitor and it's working fine using it as secondary (after finding the vista drivers)
Which version of UPDD are you running? 4.00 or 3.8 ?
Note, If you are running Vista you need to use the 4.00 drivers
Here you can download them, but they are not licensed so you will get a popup alarm ever 50 clicks.
LG is working on releasing a licensed version that will fix this.
Touch-Base - Download Centre
In 4.00 you have a page with hardware..then two options Handling monitor and connect to USB. Set handling monitor to the correct number (#2 for you)
Then hit the calibrate and you will get it on the correct monitor.