I also have the same problem as the OP. I have a 8GB Fuze+ with Sandisk 16GB Class 4 uSD that isn’t recognized by the Fuze+ but works fine with my PC’s. Both Fuze+ and uSD are less than a week old. I just contacted Sandisk tech support and they told me that they are aware of the issue and that there will be a new firmware update released in 1-2 weeks that will fix the problem.