Im always getting that UN500 Error message thing too. We have three boxes, and have tried pressing the red button on two of them - Both coming up with the said error. My signal level on the box in my room is (hope you're sitting down) 16777199. Signal downstairs that was tried for red button is 253. The third STB that has not been tried has a signal level of 16777204. These "AGC Signal Levels" appear to fluctuate every few days or so - quite strange.
Just a bit of explanation - the third box is connected directly to the little junction box that sits outside your house. This is also the case with the downstairs box (box 2). Box 1, the STB in my room is taken from a splice in the cable from downstairs - thats how NTL installed it!! Apparently it was easier and it does, I must admit save alot of black cables running round the side of the house.
Any explanations for the strangely high signal level?
To "ntlrocks" - let us know what the problem was when you find out please.
James