The issue was impairment of deferred tax assets, so that was a pre-Enron thing. As for when, that I am not sure of, but it didn’t help the Democrats that they passed this right before Q1 earnings season.
The real issue here, the one that caused the corporations to report this immeadiately, was the accounting change that required companies to account for these changes as soon as they learned about them.
That’s what brought this to the forefront during the first week post HC, and required them to include the loss during the first quarter of the year.
I’m not 100% on whether it happened because of Enron, but that’s how I recall it.