Mouse freezing randomly at Startup in Win 7

Hello, I've recently begun to have a problem about my USB mouse and my new mobo.

I've bought an MSI 990XA-GD55 3 weeks ago. I've formatted my hdd, installed a clean x64 ultimate, installed newest drivers and updated the bios. However, there began some problems at startup about my mouse. Randomly, lets say, in every 7-8 Boots, my computer doesnt recognise my mouse, saying that "device could not be installed" or something like that, you know, the default "usb device error".. And i must either re-plug it, or restart the computer..

I've changed the ports, re-done everyting, but no chance..It happens randomly, just before "Welcome" screen appears, the light of the mouse fades away, and after Welcome screen, cursor does not move..

Thinking that it would be a mo'bo issue, i've changed it with a better model MSI 990FXA-GD65. Another format, another install of the newest things, bios update..However, *** happens again!

I've got a A4 X7 XL-750BK mouse, which is kinda new and doesnt have (and had) any problem except this one. Some say, that i should change it; but i'm really confused about it, because it runs just fine and smooth..

My other system elements are X3 720 B.E, 2x4Gb Geil Enhance Corsa 1600Mhz, Sapphire Radeon 5870 V2, 1TB Samsung HDD, etc..

OH, almost forgot the add..I've also got a USB Powered Sound Card, a Line 6 UX2, and it just works flawlessly, never had such "functional" problems..

What can i do about this issue ?