Updated 3/9/10 @ 3 PM: Fiserv has posted a response via the comments, and has also contacted Brian Krebs via email with the same information.
It's good to see Fiserv trying to get out in front of this, but it's troubling that a major player would make such a recommendation in the first place.
In a perfect world, large providers of money transfers and online banking services would want their customers to be as secure as possible.
So why is Fiserv telling their credit union and financial institution customers not to update their Adobe Reader installs beyond Reader 8.1?
It seems that security updates for Reader are causing functionality issues for Fiserv, to the point that they want customers to remain on a version that's two years old.
I can't even begin to count the number of serious vulnerabilities that have been reported - and are being actively exploited - on versions through the current 9.3. Staying on the current 8.1x version is both reckless and an invitation to compromise.
Brian Krebs has a detailed write-up on his Krebs on Security blog.