I've been having a similar experience with my 4000T which was perfect until Christmas.
Then from January I'm now getting frequent gaps in the EPG.
Eg I can be watching a classic Corrie recording and I can see all the future timers on the left hand of the recording screen. Finish an episode and go back to the list of recordings to delete it, and some of the future timers have now gone. Go to the EPG and it's "no information available".
So the info is there when the box switches in but somehow gets wiped? Changing channel briefly to ITV3 then back to BBC1HD (my box is usually tuned to a HD channel) will fix it.
Something definitely has changed since Christmas - I had no problems before.