Jul 20 12:31:31 heimen-at-compaq kernel: [ 5699.773080] usb 3-2: new full speed USB device using ohci_hcd and address 3Jul 20 12:31:31 heimen-at-compaq kernel: [ 5699.987241] usb 3-2: configuration #1 chosen from 1 choiceJul 20 12:31:31 heimen-at-compaq kernel: [ 5700.111745] cdc_acm 3-2:1.0: ttyACM0: USB ACM deviceJul 20 12:31:31 heimen-at-compaq kernel: [ 5700.120880] usbcore: registered new interface driver cdc_acmJul 20 12:31:31 heimen-at-compaq kernel: [ 5700.120893] cdc_acm: v0.26:USB Abstract Control Model driver for USB modems and ISDN adapters
Misschien komt dat omdat hij op Ubuntu al gemount is? Unmount hem daar eens en probeer het vervolgens in Windows?