I am having a different issue I deposited money in my Mtgox account and I missed one number on my account and supposedly there is another user out there with the same account number as mine minus ONE number and they are saying my funds cannot not be refunded...I have just filled a small claims lawsuit against Mtgox and Bitinstant... and will file a subpoena for the information to the "incorrect" account number because it's baffling to think that a multi million dollar corporation has two different users with account numbers that are different by ONE digit and on top of that it's not like it's a different number my account just have one extra digit... ie: mine would M....888X and I accidentally put in M....88Z so now they are saying the funds have been sent and they can't retrieve them... if this is the case HOLYSHIT what a huge security issue to know that there are hundreds if not thousands of users with account numbers that are almost identical.
Diallois, I am in the same boat as you are. Actually, in my case, instead of M...(8 numbers)...X, my account number was entered as M...(last 6 numbers)...X. After giving me the run-around in (thus far) 9 different emails from support, "Danny" has finally made it absolutely clear that MtGox's position is that the money was transferred to the wrong account and MtGox cannot recover it. They claim that only Bitinstant can resolve the problem.
Putting together my situation with yours, one of two things is true:
1) MtGox has some accounts with 6 numerical digits, others with 7 and still others with 8. By both remarkable coincidence and extraordinarily poor planning, it miraculously happens to be the case that removing one number from your 8-digit account and removing two numbers from my 8-digit account number BOTH yielded legitimate, existing account numbers held by other members.
OR
2) MtGox has a policy of embezzling any funds transferred by mistake to a non-existent account number. If funds were transferred via Bitinstant to account number "UMFUFU666", those funds would disappear in exactly the same way.
I'm still trying to get their service people to clearly state this policy by email. They are quite evasive and/or incompetent, but I have already received statements that are clear enough to be useful in a lawsuit.
My situation clearly reinforces your case and strongly suggests that there are many others in the same situation. I'm very pleased to hear that you are suing them, since it appears that nothing short of legal action will persuade MtGox to abandon this policy. Please let me know if I can help.
At best, this policy constitutes a bad faith violation of their terms of service contract. MtGox has tried to be vague about the contractual basis for its relationship with customers, presumably in order to facilitate getting away with whatever they please. In order for Mutum Sigillum to obtain the licenses necessary to operate a money transfer service in the US, they would need a clear contract. Thus this issue is indirectly related to the federal case that recently resulted in seizure of assets en route from Dwolla to MtGox; in both cases, Mutum Sigillum has attempted to benefit from operating in a gray legal area instead of complying with US laws that offer consumers some protection.
I do not hold Bitinstant completely blameless, because they could trivially modify their order interface to simply reject transfers to MtGox account numbers with the wrong number of digits. I pointed this out to Bitinstant but they appear to have ignored my suggestion. This oversight clearly pales in comparison to MtGox's policy of confiscating these funds, though, and Bitinstant presumably gains nothing whenever this happens. Indeed, it is probably ultimately bad for them, since it alienates customers like you and me!
btw, My recollection is that the number in my account was listed in the 6 digit form when I first opened my account, but I've been unable to find proof of this. If anyone reading this has any info about historical changes in MtGox's account number format, I would be interested.
