Please see Bruce's reply below.
To add to it ...
To see how full the 9150T is use MENU > Record HDD Control. There is a green stack which shows how full your 9150T is. Just beneath the green stack it states the % free.
If it states anything lower than 20% free you are at a very high risk of your 9150T corrupting your recordings - past or present.
You should attempt to delete sufficient recordings to always keep it above 20% or preferably more.
Unfortunately it is possible that the programme index for your 9150T has become corrupt. This means that however many recordings you delete the % free does not increase. In that case watch all your essential programmes and then reformat the drive. YOU WILL LOSE ALL YOUR RECORDINGS.
MENU > Record HDD Control > Format.
NS
November 2013