You cant download apps from the market or you cant update them from the market? And what happened that you lost your music playing app or was it just gone all of a sudden?
Honestly at this point I am assuming you have been running UD 2.4.0 for quite some time and it may just be a good time to wipe and re install the ROM. If you would like someone posted UD 2.5.0 in this section, you could always install that since it will be a little more up to date. Here it is.