About a few weeks before Lion was released, DisplayPad support for Lion was tested and working. Then a new pre-release build came out which resulted in massive problems for DisplayPad on machines with the NVIDIA GeForce 9400M. The main bug which Apple introduced meant that if DisplayPad(or any other similar software) was installed on a system, then no 3D acceleration would function. This in turn meant that CoreAnimation did not function. CoreAnimation is used by the new login screen on Lion, and as such the login screen would just display as blank in these situations - Not good.
We investigated the problem on our end, and contacted Apple to try and get the issue fixed before Lion was released. Unfortunately this never happened. Apple put DisplayPad on their list of incompatible software on Lion and made the Lion installer disable DisplayPads extensions.
Weve been trying to find a workaround for the problem, but it seems like users with the NVIDIA GeForce 9400M will have to wait until Apple fixes the problem. Until then, weve updated the version on our website to detect if you are on one of these systems, and allow you to run/install DisplayPad if you are not. If you are a DisplayPad user whos upgraded to Lion and is no longer able to run DisplayPad, you can download and run the latest version from our website.
In summary: if you have an NVIDIA GeForce 9400M graphics card, you cannot use DisplayPad on Lion until Apple fix the bugs (current 10.7.2 pre-release still has a critical bug). In all other cases, download the latest version of DisplayPad from our website - it should work properly.