innovate error code E4

[neandethal]

Hi Folks,
during the Croft weekend my innovate MTX-L AFR stopped working after being fine in first qualifying and nearly a year from installation. It now only gives an E4 error code. Have tried re-calibrating a couple of times and no joy. It does the first phase ok on E2 but when the sensor is connected it shows HTR for 15-20 secs then reverts back to E4. Have phone innovate helpline, which goes through to Greece, so you can guess how helpful that is!!
Has anybody else had this issue and found a solution or is it swallow hard and buy a new O2 sensor?
cheers, Ian.