I had same problem and opened to see if could be cleaned and inside is dozens of little plastic cups that go everywhere. Bought new one at ASDA for LESS THAN �5. and just cannot see the point in paying more.
it may not be broken. unless its a laptop, it may be hardier than you think.
-- disconnect it from the computer
-- get some kitchen roll, and put it on some flat surface
-- turn the keyboard upside down, and rest it on the kitchen roll. leave
-- once seems to have stopped any dripping etc., turn back up, and take a damp (but not dripping at all!) cloth, and wipe the keys to stop any sticky mess
-- re-connect to computer, see if it works
unless of course, like mine, its a wireless :P then its well worth the effort of cleaning it (vs. the effort of either buying one compatible with the mouse / connector thingy, installing it OR buying a whole new lot of cra... sorry, stuff)
It will make a difference whether it was a diet brand or not. The moisture issue is not the main problem, as suggested, however the sugar in the will gunk it up for good.
No need to do anything silly and expensive like buy a new keyboard or trying to take it apart. Just unplug it and give it a good wash in the kitchen sink. Yes, I am serious. Afterwards, make sure that it is really thoroughly dried out before plugging it back into your computer again - maybe a couple of days on a radiator or hung on a washing line. The water will do the keyboard no harm at all - provided that you don't have water and electricity in it at the same time. It cleans all the gunk off the keys too.