We've bought a stack of 19" wide-screens which work at 1440*900.
We have 2 types of thin clients; HP T5720 and the HP T5700.
The 5720 supports the resolution just fine, the T5700 doesn't.
It has a Ati Rage XL PCI 8mb chip onboard.
After Googling for a while, I came across these pages...