A TV will ignore remote if set to option 0, which can happen by mistake in certain situations.
Whilst this is not common - its a bit hard to accidentally do - it is not unheard off, and is the first thing to check when a TV ignores IR , and it is certainly the cheapest to fix !!
Firstly - check your Beo4 by looking at the IR emitter via a mobile phone camera - you will see the flashing signal. Sometimes failure to respond to a command is actually failure to send, not receive. Check your manual buttons for operqation on the tv itself.
Suggest you try the following.
1. Unplug for about 5 mins.
2. Disconnect everything that may be attached - ML, VCR, STB et etc - and have a DVD to hand that you know is not scratched etc.
3. Plug back in.
4, Put the TV into Option 1 ( press list & standby together, press list to display OPTION, press GO, presslist to display V.OPT, press 1 - TV LED should blink to confirm)
Try again with the DVD.
If the above doesn't work, there is an issue inside your Tv that needs an engineer. Sadly, any repair cost (unless DIY) is nowadays likely to be more than just buying another on line.
If it does work, unplug & reconnect your other stuff.