I don't know whether others encounter such problem, but my msp430 usb mouse can not be recognized if I plug it in a pc with a mouse already pluggined in. I have tried several PCs and mice to have this conclusion. I will try to see whether the problem is with V-USB with avr mcu.
[update] Now it works with cycwin plus mspgcc from sf.net. @simpleavr, Could you help let me know the toolchain info for the project? I am using CCSv6.1 plus msp430gcc_184.108.40.206 and downloading hex files using FET430 pro lite. It is OK if I download your hid hex directly. So it indicates that h/w wiring is OK, however the mouse can not be recognized if I compile the source files to .out file then download it using CCS.