just wanted you to know that GQUSBprg 6.13 and GQ 4X on linux (ubuntu 10.04) with virtualbox 4.0.12 and windows xp 32 installed works very well. Here is what I did to get it work.
1)I had to add my ubuntu username into the group vboxuser. (go into administration-users and groups- manage group... click vboxusers and chose your name. THEN log out and log in back)
1.5) Ensure that USB connection are checked in virtualbox configuration prior to start windows xp.
2) Start windows xp and then install the software
3) Plug the GQ-4x to the computer (it will install the drivers)
4) When finished open de software and when it says.. detecting interface, remove zif blablabla... just right click on USB connection in bottom right corner of virtualbox windows (right beside network icon, cd icon, hard drive icon, etc.) and click on the GQ USB controler. The software will now detect everything.