I was informed that they are forbidden to provide information about why my money is being held for 3 months or when will the money be released.

I'd hypothesized that Mt. Gox could be restricted by a gag order, but it seemed to me unlikely that an investigation/harassment would rise to that level particularly given the jurisdictional issues. I'm not aware of how (and if) gag orders are implemented when driven by the Japanese of course. If Japan was pressured to apply U.S. gag order practices to Mt. Gox it would be a very interesting development...even considering their Mutum Smegma or whatever wing of their operations.
If there is any truth to this statement and I had any criminal dealings that could be elucidated by data that Mt. Gox holds, I'd be shitting a brick and thinking about acting upon any exit strategies which may exist.
To my knowledge, a gag order does not require that one lie to their customers (e.g., 'we hope to get new banking partners working in several weeks') so even if they are under a gag order I still feel that they've done me wrong and I'll not forget it.