I haven't been able to reproduce the problem in my 8GB card, but anyways i think the reason is literally that the memory stick was not ready in the time plugins are loading, althoug the memory stick modules are loaded, but they require some time to initialize as they are executing code in other thread. The code in 3.80-3.90 of plugins loading is same, it was probably the change of sony ms driver what altered timings, etc.