Ring in and book an engineer to cone out is the only way. A new box won't cure the slowness - that's a software issue which they're so say working on- but should stop the freezing. They may check your signal first because if that's the issue they can sort it out with a new box.
My tivo box has been playing up for a while now, we had an engineer out who said he found a problem with the cable outside but we still get alot of picture freezing and we cant risk watching or recording on HD because the programmes are unwatchable, also twice now we have lost our tv guide and favourites and i have had to reconnect. Very frustrating.
Can you reboot the set top box after reading this message? If you're still experiencing issues after that then we'll be able to take an accurate look at the hard drive to see if we're detecting any errors.
Does this happen on the majority or minority of recordings?