Apparently Fidelity's benefit administration services division screwed up 22,000 GM employees and retirees who no longer have benefits (temporarily). Now, I don't usually comment on benefits administration, but as this is part of Fidelity's larger HRO offering, I will. I don't have a link for you, but it's an Associated Press article titled "Computer Glitch Cuts Benefits for 22,000 at GM."
There are probably a couple of contributing factors (all of the following are my assumptions based on experience).
First, GM probably forced a fast implementation. Fast implementations when there is complexity and a huge population are very risky. There simply isn't enough time to test and audit. Unfortunately, when a client is this big, they can demand fast implementations as part of the sales negotiations.
Second, Fidelity's main obstacle seemed to be a lack of control and process around their data import/data conversion from the previous systems. You'd think that they would be good at data conversion, but apparently the conversion dropped employees, dependents, reitrees, etc... (ouch - retirees without benefits).
Bottom line: in major implementations, take it slow, audit well, put in solid process change around the new technology. Without this, you are setting yourself up for failure and termination.
As if GM doesn't have enough problems already, the UAL said "virtually anything that could go wrong, has."