This has been going on for months. If Mt. Gox really wanted a high-volume banking arrangement, they would have found one by now. But they seem to find having excuses for non-payment more useful. This suggests they don't have the depositors' money.
While it is very likely they have less then 100% of client's funds on deposit, we really don't know if they are insolvent. If most banks deem their activity as high risk, they may not be able to set up a relationship that meets their needs in a reasonable time frame.
Either scenario is certainly possible, we cannot (currently) say for certain which one it is.