It seems that United's websites in many countries are "undergoing website maintenance "

If you look on the top page of the UK website, you will find the following message (with an annoying, flashing "Hazard Warning" symbol):

Dear Customer
We are currently undergoing website maintenance and are unable to process your booking request at this time.
Please contact your local United Reservations office for further assistance..

Bottom line - The only way for you to get around this is to call the reservations number.

BTW - I have had the same issue with the UA website in Japan since before Christmas 2005. My comment is here:
http://www.flyertalk.com/forum/showt...airlines.co.jp

Also, another poster mentioned that he's having the same problem with United's website in Singapore.

United must be losing revenue due to this SNAFU. (I've already booked one flight with the competition because of this). It really is a shame.