Has O2 disabled wifi router phone tethering?

When I upgraded my HTC desire to froyo a few months ago, I used wifi tethering a little bit for when I was stuck in hotels etc,

I've just tried connectig on two different laptops and I can connect to the phone via the computer, but cannot access the internet through it,

Have some setting changed? Does tethering still work with O2?

Just wondering! Would be a great shame, as I loved that feature,