Apparently, the cause for all this is the new BlackBerry Balance software feature, which aims to create two separate experiences on a single BlackBerry 10 handset - one for business and one for personal matters. It's not yet clear exactly why this feature is causing problems.
The security levels which these devices are trying to reach aren't the highest possible. BlackBerry 7 and iOS, for example, have managed to obtain clearance for use in the "restricted" security level, and that is said to be two levels below the top "secret" security level. Unfortunately for BlackBerry, BB 10 will not be allowed even in the "restricted" level for the time being, which is really bad news for the company, as the government sector is one of the markets where it's been traditionally strong, and it's not like it could afford to lose any customers right now, especially when it comes to those beefy government orders.