Which screen is "wrong" is up for discussion, however in my configuration I have dual screens, one of which is designated as the "primary" display in GNOME display settings. Starting tlclient always launches it on my "secondary" display, even though the mouse pointer is on the primary one. Placement of the window should be left up to the window manager, and I know there is a lot of turbulence in the GNOME community about window placement and desktop handling, so it's possible that there is no sensible solution to this anyway. Perhaps it's worth a look to see if we're doing thing correctly, though.
Doing this work on bug 4275. *** This bug has been marked as a duplicate of bug 4275 ***