1 of 10 withdrawal attempts from MtGox bounces due to wrong information (wrong account number, wrong owner, wrong SWIFT address, etc), and all of the bounces have to be handled manually by their bank. This is what overloaded their old bank. They will have to work slowly through the queue to avoid too much work at once, but hopefully at a much faster pace.
This is exactly what I call a lame excuse. It sounds ridiculous for anyone who knows how a modern bank works. I can hardly imagine that you can overwhelm a bank with wire transfers. Actually, this is the way the banks make money. It is as mtgox would not let you trade because you overload their system with you trades.