20th June: Website now working again! - and after 21 years UBT is still here and we continue to crunch :-) (PS: I still have no idea where the UBT logo went !)
WCGs mission is to create the largest public computing grid benefiting humanity. You can choose from various work units to crunch: Fight AIDS, cure Cancer or support the Human Proteome Folding projects amongst many. (Previously supported by IBM).
It happens when 1 or more of the WU results don't agree with the others. An extra WU is sent out to get a quorum that agree. If you are in agreement with the others you get full credit. If your result is out of step you have a failed result and only partial credit.
Thanks for the clarification John, as you can see I am a newby to this "crunch" activity, just got in from work and found two of the offending wu's have now been validated :)