I just want to pass on a tip to anyone who might find themselves in the same position as me. I have a new motherboard (Asrock 880GMH/U3S3) which comes with Xfast USB. Problem I had is that when I connected my Nokia 5800XM via USB in file transfer mode and tried to access any of the folders the computer hung and had to be restarted. I thought it might be a FAT32 file format problem but the microSD card from the phone in a card reader has no problem.
The solution is very simple - run the Xfast utility programme on the PC and select 'normal' ('turbo' is the default). It should remember this setting so next time you plug in 'normal' is preselected.