OK . . ignoring the "flatulance generator" for the time being

have you tried a spare key if you have one ? (guess you would have tried that if you have though)
If not I would also suggest as Dbug says remove your power sounder from under drivers scuttle .
Possible fire risk, so remove & leave off ( as most do on here ) or get a new one . (see disconnection/removal in maintenance guide)
Then try key re-sync . ( did re -sync operate correctly when you did it previously . . . doors locking & un-locking etc.? )
If you have to take the key apart again . . be careful of the very small imobiliser chip that sits in the horseshoe part of the key .
If it is loose & drops out as key is pulled apart car will not start at all. And hard to find if dropped on the floor /carpet/driveway etc.
It would also help future diagnosis if you update your details with your omega model ,year & engine
HTH
