I have the exact same problem with my nokia E5-00. Have used the ovi suite, pc suite and connect pc to net softwares but all have the same thing to say, cannot detect the device or locate drivers. I downloaded the lastest nokia suite from the official site yesterday. The required nokia drivers required for usb cable connectivity are installed in the phone memory. I download the driver manually in the pc but it didn't help. It seems to be a hardware problem to me. If there's any drivers to be downloaded please let me know.
On the other hand, if you try using the connect via bluetooth feature in the Nokia Suite, it works smoothly and you can browse the net on your pc at 2g speeds. I want to use 3g so I think I'll need to have the usb cable working for that. Please help!