My guess is that router isn't upto the job, so i recommend buying a Linksys WRT54GS as this
should work fine and alot of people currently use it on this forum. With 10mbit being upgraded to 20mbit in a few weeks you should change the router to give yourself the best chance of everything working properly.
There is an Easter offer at
www.pcworld.co.uk for it at £39.99 so you may wish to consider that.