finally, someone who has the same problem like mine..
bro, i faced similar issues 2mths back..
1. suddenly the PVR recorded unintended shows (mine was Tarzan).
2. PVR starts to slow down, changing channels took almost 3-4mins before the channel changes.
3. Cannot record shows (randomly showing 'recording failed').
so i changed mine, also same like yours, since >1yr, i do not have warranty already
but they change for free. the only thing is that, all your recorded stuffs are now gone with the old PVR.
and after 2mths using this new PVR.. now it happens again..
the new PVR starts to record unintended shows, even to the extent that
the red LED 'record' is on, but no new recording entry..

wah same symptoms like mine...slow down...recording led light up...dang ! anyway which pvr decoder you change to?
so i guess this has nothing to do with PVR...like anon say its a software glitch...