That sounds strange to me again
My w810i is a lot more pickey when it comes to my fake Memmorysticks
It does not save photos in the highest resolution to them
(i guess they are to slow)
but my PSP loads Isos just fine from them...
if you copy files via the usb 1.1 to your MS are they readable afterwards?
For me the PSP is my most trusty card reader (my cheap 16/1 reader corupts files sometimes and the w810i only works as usb 1.1 device)
at the moment i belive your Memmorystick slot in the PSP is broken o.O