After upgrading one of my lab systems to 1.4(1i) (released December 20, 2010), all of the fans in my chassis showed as failed. Since each fan module contains two separately monitored fans, this resulted in 24 total warnings in my system (8 x fan module, 16 x fans) – annoying, but cosmetic only.
UCSM 1.4(1j) was released just a few weeks later (January 7, 2011) with a number of small bug fixes listed in the release notes, but nothing about my fan issue. However, after updating my IO Modules to the new 1.4(1j) code, the errors disappeared. This makes sense, since the IO Modules contain the Chassis Management Controller which is responsible for monitoring all of the chassis components.
So, thanks to Cisco for fixing this small but annoying bug!