There is a little trick you could try first, try wiggling or rolling the batteries in the remote before replacing them.
Yesterday I went to change channels and nothing happened on my 4000T, then I noticed the light on the power button on the remote was flashing very dim. So before replacing them I just rolled the batteries round and the remote sprung back into full power.
Sometimes its not the batteries it just the connection on the battery terminals. This happens every now and again on my other PVR.