I had similar problems with my pce-n15 repeatedly dropping connection to my Virgin router, even though all my other devices connect to it fine. The drivers wouldn't even install from the disc. I can offer one suggestion if you are using a Windows operating system.
I seem to have resolved this only through Windows. I uninstalled and reinstalled the Asus software from the CD several times. However, on the last attempt, when it offered either Asus or Windows, I chose the option for using Windows wireless instead of the Asus utilities. When I connected to the Virgin router after that my connection was maintained just fine and (touch wood!) has not dropped yet.
Hopefuly that might help, as I had been trying for days to sort out the connection! I can only assume there was some unseen conflict between the Asus and Windows software. Bypassing the Asus software appears to have resolved it for me.