Not sure if this is a common known thing or not.. I just found it by accident the other day...
I have been using Maya with dual monitors (NVIDIA) for ages - and have always had a problem when running the UV Editor in the second window (Maya main window being in the primary). The problem, is when you click and hold the RMB to get the selection window (inside the UV editor), the menu appears on the edge of the primary window, NOT under the cursor in the secondary window..
I know one option is to set NVIEW so that it treats both monitors as one big monitor, instead of two seperate ones - but I don't like that too much...
Anyhow, to fix the problem, open up the UV window, and in the top window bar (the blue bar at the top of the window), click the Maya logo icon on the far left - and UNCHECK "attach to main window".
Now the RMB menu for the UV editor will appear under the cursor when the UV editor window is on your secondary monitor.