Updating your avatar doesn't work currently (unless you use a link to a web-hosted pic, IIRC). Mail us at whathifi@haymarket.com, with subject 'dave k avatar' and Mr E will sort it.
As for biog - are you updating your signature? If so, I'd recommend not putting any hyperlinks in it (ie http://blah blah) or you'll get yourself deleted. Some older forum users are able to do it, but newer ones are not - spam avoidance I'm afraid.