I have a problem with the 'PlayOnLinux install menu' as in the window cannot be resized and the 'install a non-listed program' icon is off the bottom of the window - is exactly the same problem as in the link. I'm on Lubuntu 14.10, only happened since I upgraded from 14.04.
The post on the other forum does us no good. We only look at stuff in this forum. The POL install menu does not resize, and if you cannot see that link, then something changed in LXDE (the desktop environment) in the new Lubuntu release, or you have a theme or fonts applied that are pushing it off screen. It is visible on every other OS, so it is something with how your system is showing it. Make sure that you are running a default theme with default settings. That link that you posted has them all talking about tweeking the window manager to show it, which means that it is not POL that is causing the issue; your distro's window manager is cutting it off.