Are you positive theupdate didn't do any damage? I had a similiar issue where evrything worked but not disc channel. I did it myself though trying to install wads from 249 , I uninstalled something and... long story short I had to redo the steps of my mod removing the stubbed ios and reinstalling cios 249( steps 4 and 5 of my mod). You should wait for confirmation from a more experienced person, but it worked for me on 4.2U. If you have priiloader installed you can go into system hacks and disable "force disc to play from ios 249. This may help in determining if it is a problem with the cios 249, if the disc will boot then.