Hello,
I have found this:
I have internal MS reader in my notebook (mapped to G:\)
I have connected my W300i by Infrared port.
If I insert MS into the reader, I can see it in memory status section of MPE.
If I put MS out, then g:\ drive is not visible there.
screenshot here : http://www.tekl.com/mpe.jpg
This MS is formatted by K750i. It contains MSSEMC directory on the root.
I think, that if there is Memory stick with MSSEMC directory in the system then MPE expect, that it is connected from mobile phone (although it is not). I don't know, if this can be solved.
btw. I was not able to test, what happens, if I have MS inserted and phone connected by data cable at the same time.