Ever since updating the ROM on the "not very good as a phone" X1 it's been unable to play iPlayer live with sound.
There doesn't seem to be a fix available and the Vodafone web site is not particulary helpful.
What does seem to be a solution is to download the SkyFire browser. This has some annoying features like a reluctance to save bookmarks but will play iPlayer with sound.
The only caveat is that you have to make sure it connects via a Server in the UK. If it doesn't iPlayer will not let you connect as it will think you are outside the UK.
If you get this problem after installing Skyfire, check the Server it is connected to by Menu -> Help -> About -> More Info.
If the Server address starts with 10.110 it has connected to a UK server and iPlayer should work.
If it is anything else it has connected via the US and iPlayer won't work. To fix this you need to delete the Prefs file in Application Data \ Skyfire and reconnect and repeat this process until it connects via a UK Server.
Once this has happened it should always use the UK server unless it is unavailable.
I'd recommend taking a copy of the Prefs file just in case.
BTW, one you have started Skyfire, IE and Opera won't work until you exit Skyfire and force the data connection to Disconnect.