Borrowed this from the Hyatt site. I don't have any reason to doubt it.

Topic: Y2K Problems at Premera Blue Cross

MSC/Premera Blue Cross issued the following letter to employer groups on Feb. 7th. Like many companies and agencies, they took the "don't tell until after it's fixed" approach. Dear Member:

In September of 1999, we transitioned to a new claims processing system to comply with Y2K standards as well as serve you, our customers, more efficiently.

After the conversion, we learned that a number of claims for your account were being processed incorrectly. We immediately suspended these claims to ensure that we did not continue to pay the claims incorrectly. We have completed the system corrections and claims are now being processed in a timely and accurate manner according to your benefit plan. Services suspended within the time period are now being processed and you will be receiving an Explanation of Benefits (EOB) within the next few weeks. If you had a claim processed incorrectly prior to the suspension of the claim system, your claim will be reprocessed and you will be receiving an updated Explanation of Benefits (EOB) within the next few weeks.

(snip)

It looks like they have to review every claim submitted over a five month period and reprocess who-knows-how-many, all the while continuing to process current claims. Glad it's not MY job!

-- Martin Thompson (mthom1927@aol.com), February 10, 2000