I realise this thread is somewhat stale, but this problem has not gone away, and the issue with the FVP 5000T, and others, remains.
Following the suggestions on this forum, I have reduced the 220+ Freeview channels on my Humax box to under 80, and this has improved the ability of the device to show programme information, especially that for future programmes which was often 'not available' no matter what steps I took.
I asked Humax in the UK for their suggestions, and they said that this is now their suggestion when this problem is encountered. They also confirmed that the FVP5000T is capable of holding at least 200 channel epg information, but suggested this could be reduced due to 'some signal issues'.
What I find particularly frustrating is that my relatively elderly Panasonic EX97 , which is NOT connected to the net, but relies solely on aerial signal information, is quite capable of storing all epg information on all available Freeview channels, despite being fed by the same aerial, and has NEVER shown the 'information not available'message. Perhaps I should experiment , retune my Humax, and then disonnect the device from the net?!