Injector 4 problems!!! Need desperate help!

Hi all,
I have an '04 1.4 C3, that suffered from a failed injector (Number 4). I replaced this, and the car runs fine for about 2 miles, then petrol leaks out from the injector (looks like from the fuel rail).
First time, it looked as thought the rubber seal was not in properly, so strip down, refit, rebuild. Does the same again. To eliminate the injector, I swapped the injector, but this did not work, as fuel still leaks out after approx. 2 miles.
The injector is a Sagem injector.
The engine management light is on (from the original fault).
I am at the end of my tether now, as I can't seem to resolve this. I can't believe that two injectors are failing (they are not when swapped to another location, which, by default I would assume the O-rings are good).
Has anybody come across this, or has a fix for this please?

Thanks in advance,
Johny247

Johnny247 wrote:I swapped the injector, but this did not work, as fuel still leaks out after approx. 2 miles.
The injector is a Sagem injector.

Leaked from the same injector or the same location (no.4)?

Johnny247 wrote:I would assume the O-rings are good

I would just replace the o rings, as they are not designed to be reused.