mikeL,
The 14" -er is a TV - I referred to it because it has a similar problem and it uses a Trinitron tube, just like my monitor... I wondered if this could be a Trinitron feature...
I have speakers next to the monitor - about 10" away from it, but they are shielded - or so are advertised... on second thoughts they were rather cheap, but the sound is good. anyway I removed them - back to headphones
If this was caused by the speakers, will the monitor get back to normal?
Cheers