I am having problems with my Pi and connecting anything to the spare usb port. I use a Xenta wireless keyboard and mouse, (supplied by ModMyPi) so the 2.4GHz dongle occupies one usb slot. I f I connect any usb drive to the second usb slot, powered or not, the mouse behaves badly, the pointer, going to the bottom of the screen, and doing it's best to stay there, becoming unusable.
This means having to unplug any attached drive and plug in a wired mouse to continue, or shut down. I have checked the voltage at TP1 &TP2, and it gives between 4.99v and 5.2v without any usb drives attached, then dropping to 4..93 volts minimum with a usb device attached, then the mouse goes awol. It seems not to be a power supply problems with those figures.
The keyboard is unaffected. It's very irritating, and using up all my time just trying to do anything useful with it.(and failing)
Perhaps related, I don't know, is that openELEC freezes every time I try to use it, and I have lost the system partition on a couple of cards then the card becomes unreadable by any device I have tried (Windows Vista/ XP / Linux Mint Laptops and my Nikon DSLR which says no sd card inserted) I've spent £25 on sd cards for it!
All I have is a device that can show a few apps and a web browser on a tv screen, what's the point in that?( It can't even print, my wife rolled her eyes as if to say "what a waste of money") and I agree.
I have tried Raspbian, Debian, PiBang and also varying degrees of failure with openELEC and Xbian.
Can anyone point out what I am doing wrong here? It must surely be down to me.