i have the same error, and i think i have nailed down the case when it occurs... this error only happens if you try to record a show which is kind of duplicate in your epgHi,
For the last couple of months, I always get "Parameter EndTime not found" when trying to schedule recordings. Has anyone else got this? I've even tried a fresh install of the TVService, Database nd MPWebint. I'm using the Radio Times EPG Grabber.
e.g. i have 2 channels with exactly the same program (only difference is that that one is SD and the other HD), i can't schedule any show on both of this channels, always getting this error... ...i will file an issue on google code for this..