"We're in the process of adding some new features to WaMu.com," said bank spokeswoman Olivia Riley. "Unfortunately, the work that we're doing is taking longer than expected and is causing some online features to be periodically unavailable. Most of the site is operating just fine, but we're not quite done yet. We apologize for any inconvenience this may be causing some of our customers. We are working diligently to finish up the work we're doing and look forward to offering our customers some great new online banking features."

Initially, Houston resident Matthew Castillo said the bank's site was unavailable, but on Wednesday he was able to log into his account. "I can log in, but I can only view my balances, none of the other functions are working. But this is still the best functionality I've seen from them in days," Castillo said.

"Since Sunday, the account login has been unavailable, with a 'service not available' server error, or a customer care error message, depending on the phase of the moon I assume."

On Friday, Castillo said that while the account login function is working, the bill pay function is still down. "This is crazy," Castillo said. "I don't own any paper checks. It seems to me they should have rolled back days ago after they found out it wasn't working."

Castillo and others who are chronicling their problems at haacked.com said they think the problem is due to an ASP.Net upgrade. Riley, however, said it had nothing to do with .Net.