Several Digital Spy forum members reported not being able to access ITV HD, which is available via the red button on ITV1 when a HD programme is on, during Harley Street.
The decision to broadcast the high-profile Paul Nicholls series in HD had been hailed as "brilliant news for Freesat customers" by the TV service, with which ITV HD is exclusively available.
Some posters were able to watch in HD having tuned to a different regional variation of ITV1, by entering an incorrect postcode to their equipment.
Ten of 21 ITV1 regions were added to the Freesat electronic programme guide earlier this week.
Sparksman, a forum member from Chesterfield, noted some irony: "We spend the last nine weeks with ITV London as default, then we finally get our own region, promised in June, half way through July, only to find we have to re-tune back to London to get HD!!!"
Other problems reported included varying picture and sound quality, and failing to revert to ITV1 once the HD broadcast had finished.