Don't know too much about it but they made poor managerial appointments after the CL win and starting spending above their means bringing players in on absolutely huge wages. Ended up slipping down the league and constantly changing managers whereas the 'big name' players earning huge pay packets weren't performing at all and happy just to pick up their wage every week. Completely put them in financial ruin. Ended up with them nearly going under in 2002 (I think).
Ever since then they've had a different approach of being a lot more cautious with their money, it's only really changed in the past 2 years or so where they have started spending big transfer fees again but this is money mostly recouped from player sales and good league/cup/European campaigns.