50% of the Time PDA connects as Unknown USB device

Currenlty I am using an Asus A626 PDA with windows mobile 6 as well as Windows vista buisness 64 bit. Half the time when I plug in my pda it recognizes it as a PDA, the other half the time it says it is an "unknown usb device" after which I can only get it to recognize it thorugh multiple rebootings and replugins and disabling the port and renableing the port.

Does anyone have an idea why sometimes windows vista would not recognize the device, but sometimes it will?

I had the same issue on my HTC Wizard (T-Mobile MDA) running winmo6. i got a little program that changed the mode that the phone communicated in and the problem was solved. i forget what the program was called but i got it from the forum at http://www.xda-developers.com