Slow startup on some channels - box fault?

[Aragorn]

I have an old Samsung STB which does the job OK mostly.
Recently though when it is first switched on (from standby) it take several minutes before some channels appear.
ie If we turn it on and it was previous on BBC 1 or 2 that will show immediately but if we then change to Dave or CBeebies (as examples) we just get a black screen, sometimes with 'blocky' audio, for a few minutes. Eventually it will start working but toddlers are not known for patience.
Is this a symtom of a faulty box or is it more likely a signal problem?
If the box is faulty and needs replacing, are Samsungs replaced like for like or can we request an HD 'Ready' VBox?

[Peter_]

I would ring up as it sounds like it is faulty, they will probably replace it if found to be faulty with a Cisco Vbox which can be upgraded to HD for a fee which is £49.

[Aragorn]

Hmm, it had to be power cycled yesterday (VoD hung) and now it appears to be working OK. I guess a software issue but if it starts happening again I will call it in. Thanks.