Connecting v300 to pc

Hi

I just received my v300 data cable, but have been struggling to
connect the phone to my pc. I'm using the demo version of mobile
phone tools on the cd that comes with the v300, on windows XP.

The first time I plugged it in, it did connect but I couldn't transfer
a mp3 from the pc to the phone (no error, just nothing happened);
also, even though I do have photos on the phone they weren't listed in
the mobile explorer and so I couldn't try to transfer them to the pc.
I did manage to backup my phonebook, though.

From then on, it just won't see the phone at all. If I go to the
device manager, I see the Motorola USB modem listed under Modems, but
it says that it can't communicate with the modem.

Any ideas?

Thanks
CJ