I got an email from Drewc saying my complaint on here had been forwarded to the backroom boys. But no further queries from them about what the problem was. So some attention is being paid at least.
I'm just wandering in from the old PC at home this morning, also Vista 32bit and FF 22.0 - and it seems to be working. So either the ads have been fixed, or there's something weird wrong with my office PC.
Or I suppose it's possible there's something weird wrong my home desktop meaning it doesn't display the bug even though it should...