OK I had this problem on a Compac PC. It definatly had USB 2 but was running at USB 1 speed.
Searched through the BIOS and found a button to turn on the USB 2. Guess what, it didn't help.
Went back into the bios and found a second USB 2 button burried in a sub menue of Advanced Features. It was set to OFF. Turned it on and, USB 2 in all it's glory.
So... Go through your BIOS with a fine tooth combe, check every menu, every sub menu and every sub sub menu. Somewhere, burried deep, you'll find the elusive USB 2 on/off button.
The things I don't understand are; Why is USB 2 set to OFF as Default and Why would anyone want to set it to USB 1, Why did they even provide the option? It's like selling you a 2MgHz PC with an option to set it to 2KHz.