E*Trade (ETFC) tumbled again Monday after an analyst advised investors to sell the stock, citing deepening problems at E*Trade’s banking unit. Bank of America analyst Michael Hecht cut the stock to sell from hold, saying problems in E*Trade’s home equity loan portfolio could result in billions of dollars of losses. Adding to the company’s worries: online trading and retail banking customers have been fleeing E*Trade amid concern about its toxic mortgage holdings. Shares tumbled 14% to $3.94 — putting the stock down more than 20% since Citadel agreed last Thursday to pump $2.55 billion into the company.E*Trade also continues to look less than razor sharp on the disclosure front. This column wondered last week why E*Trade hadn’t filed its current report on form 8-K following the announcement of the Citadel transaction, which came as E*Trade announced a CEO change and a writedown of more than $2 billion. A spokesman indicates the company has four days following the announcement of the transaction to file those papers, and adds that E*Trade expects to make the filing in a timely fashion. It’s almost unheard of for a big company to fail to file an 8-K on a big transaction within a day of its announcement, but then again, this is E*Trade we’re talking about. In the meantime, the big question is how low can E*Trade stock go.

E*Trade (ETFC) continues to slide, a day after it announced a big bailout deal with vulture-oriented hedge fund Citadel. Much was made of E*Trade’s success in getting out from under a deteriorating $3 billion mortgage portfolio, albeit at the deeply distressed price of 27 cents on the dollar. But E*Trade stock fell Thursday and it continues to give up ground Friday as investors worry about assorted other issues, including the company’s still substantial home equity loan exposure. As Phil van Doorn writes on TheStreet.com Friday, E*Trade has $2.4 billion worth of home equity loans in which the loan-to-value ratio is above 90%. With house prices falling sharply, it’s all too likely that many of these loans will end up defaulting — and the potential for recovery appears low.

Meanwhile, E*Trade still hasn’t filed its current report on form 8-K with the Securities and Exchange Commission, which is unusual given that yesterday the company reported three separate events that would seem to call for that sort of disclosure: the departure of its CEO, a transaction that gives one shareholder 20% of the stock, and more than $2 billion in writedowns. E*Trade didn’t immediately return a call seeking comment.

Update: A Citadel spokeswoman says an E*Trade investor relations rep tells her he expects the filing to be made in the next day or so.