I have created a file upload page with an Asset Builder page.
The problem is that the code generated by Matrix for the form element triggers the peekaboo bug in IE6 - I haven’t had any success in applying hacks to the container div.
Is there any work around to this?
The peekaboo bug is CSS specific – the HTML code generated doesn't include any CSS (AFAIK, but I guess the developers can come along and slap me if I'm wrong), so I can only assume your design's CSS is causing the error. 
Thanks Avi, I have just tried to recreate the problem using a plain design and it isn't happening there, so it is as you say.
Only problem is that I thought the bug was caused by 'float' in the css - I am not using float anywhere???
It may be a variation on the peekaboo bug, I guess. Amazingly, I was solving this exact problem for another client this afternoon (the one that dare not speak its name!) and the line-height workaround seems to have done the trick.
Though, I'm not entirely sure how you get your design to look the way it does if it doesn't have any floats anywhere…